Two masses m1 = 2.0 kg and m2 = 4.0 kg are attached to each other via a red cord that runs over a pulley as shown in the diagram below. Mass m2 is allowed to fall to the ground from a height h = 1.0 m as shown in the diagram. Assume both the pulley and surface of the incline are frictionless and both the string and pulley are massless and answer the following questions in SI units to the correct number of significant figures: a) as mass m2 falls what is the acceleration of the two masses? (5 marks) b) calculate the velocity of the masses just before mass m2 hits the ground using the law of conservation of energy ΔK + ΔU = 0 where ΔK is the change in the kinetic energy, and ΔU is the change in the potential energy, of the two masses. (5 marks)
An object of mass m1 = 2.0 kg slides down a hill. Its speed at the top of the hill (position A) is 5 m/s. a) What is the speed of the object at the bottom of the hill at position B? Assume there is no friction. b) At point C, the object hits a second, stationary object which has a mass m2 = 3.0 kg. The two objects stick together after the collision. Find their speed right after the collision. c) The combined objects hit the spring and compress it before they stop. How much does the spring compress? The spring constant is 250 N/m.
The picture below shows a rollercoaster. Which statement is correct, if air resistance and friction is neglible? 4 The kinetic energy at Point C is the same as the kinetic energy at Point B. The potential energy at Point A is lower than the potential energy at Point C. The potential energy at Point C is higher that the kinetic energy at point C. The kinetic energy at Point B is the same as the potential energy at Point A.
Three charges are shown in (Figure 1). Suppose that a = 2.2 cm. Figure 1 of 1 Part A What is the magnitude of the force F→ on the 5.0 nC charge? Express your answer with the appropriate units. F = What is the direction of the force F→ on the 5.0 nC charge? Give your answer as an angle measured counterclockwise from the −x-axis. Express your answer in degrees.
A block of mass m1 = 3.70 kg on a frictionless plane inclined at angle θ = 30.0∘ is connected by a cord over a massless, frictionless pulley to a second block of mass m2 = 2.30 kg (Fig. 5-52). What are (a) the magnitude of the acceleration of each block, (b) the direction of the acceleration of the hanging block, and (c) the tension in the cord? Figure 5-52 Problem 57.
P71. Figure shows two blocks with masses m1 = 20.6 kg and m2 = 61.2 kg; the blocks are free to move. The surface beneath m2 is frictionless and the coefficient of static friction between the blocks is 0.36. Find the minimal force F required to hold m1 against m2? (749.53631 N)
The blocks below are released from rest. The surface between block B and table is frictionless. If MC = 7 kg, MB = 5 kg and MA = 2 kg, calculate the tension in the right rope.
A 1.2 kg object hanging from a spring of force constant 300 N/m oscillates with a maximum speed of 30 cm/s. (a) What is its maximum displacement? When the object is at its maximum displacement, find (b) the total energy of the system, and (c) the gravitational potential energy. (Choose potential energy as zero when the object is in equilibrium). Please insert number PLUS correct unit
P2. A hockey puck of mass 0.2 kg is travelling to the left with a velocity of v1 when it is struck by a hockey stick and given a velocity of v2 as shown. a) Draw the impulse-momentum diagram of the puck at this instant. b) Determine the magnitude of the net impulse exerted by the hockey stick on the puck. c) Determine the magnitude of the net force exerted by the hockey stick on the puck if the interaction occurs in 0.002 s. Note: In solving the problem, take v1 and v2 as
Although friction is not a conservative force, if we make the friction force an internal force, we can still treat the effects of friction as causing a change in the system's energy, rather than as a work term. Whenever friction is an internal force, we say that it causes a change in the thermal energy of the system. For the situation of the block sliding across the floor described above, what is the change in the thermal energy of the block-floor system? +1 J −1 J It could be either +1 J or −1 J; we don't have enough information to determine which.
Two forces F→1 and F→2 act on a 3.00−kg object. F1 = 25.0 N and F2 = 12.0 N. a b. (a) Find the acceleration of the object for the configuration of forces shown in Figure (a). magnitude m/s2 direction - (counterclockwise from F→1) (b) Find the acceleration of the object for the configuration of forces shown in Figure (b). magnitude m/s2 direction ० (counterclockwise from F→1)
A person with a body mass of 70 kg is standing at rest on frictionless ice. They are also holding a 5 kg watermelon. Suddenly they heave the watermelon away from themselves at an angle of 35 degrees above the horizontal, and with a speed of 5 m/s. How fast are they moving along the ice after they have thrown the melon?
A sled is being pulled on a frictionless icy surface, by a rope that is angled 45 degrees above the horizontal. The tension of the rope is 100 N. The sled is 50 kg. On top of the sled sits your pack of supplies, which has a mass of 20 kg. What is the coefficient of static friction that keeps your pack on the sled as it travels? Give your answer with three significant figures.
A solid sphere with radius R = 4.00 cm has uniform density and mass m = 1.88 kg. It is released from rest at the top of an incline as shown. The coefficients of friction between the sphere and the slope are: μs = 0.50 and μk = 0.30. a) Find the linear acceleration of the sphere down the slope using Newton's 2nd law (hint: look at linear & rotational equations, since rolling uses both kinds of motion). b) What torque is produced by the frictional force? c) What is the angular velocity of the sphere when it reaches the bottom of the slope?
In the figure a butterfly net is in a uniform electric field of magnitude E = 5.3 mN/C. The rim, a circle of radius a = 6.4 cm, is aligned perpendicular to the feld. The net contains no net charge. Find the magnitude of the electric flux through the netting.
The square surface shown in the figure measures 3.3 mm on each side. It is immersed in a uniform electric field with magnitude E = 2500 N/C and with field lines at an angle of 35∘ with a normal to the surface, as shown. Take that normal to be "outward" as though the surface were one face of a box. Calculate the electric flux through the surface.
A 3.0 kg block is pushed along a horizontal floor by a force F→ of magnitude 31 N at a down ward angle θ = 40∘. The coefficient of Kinetic friction between the block and the floor is 0.27 . Calculate the magnitudes of (a) the frictional force on the block from the floor and (b) the block's acceleration. (a) Number Units (b) Number Units
A small rock, of mass m = 1.6 kg, swings in a horizontal circle of radius r = 60 cm using a light string of length l = 90 cm as shown in the figure. What is the angular speed of the rock?
Two forces, F→1 and F→2, act on a 3.00 kg object, where F1 = 20.0 N and F2 = 10.0 N. (a) (b) (a) Find the acceleration in figure (a). magnitude m/s2 direction - (counterclockwise from F→1) (b) Find the acceleration in figure (b). magnitude m/s2 direction - (counterclockwise from F→1)
Find the mass of water that vaporizes when 4.71 kg of mercury at 213∘C is added to 0.300 kg of water at 94.0∘C. Number Units
Find the mass of water that vaporizes when 4.46 kg of mercury at 206∘C is added to 0.325 kg of water at 98.4∘C. Number Units
As shown below, if F = 70.0 N and M = 5.00 kg, what is the magnitude of the acceleration (in m/s2) of the suspended object? All surfaces are frictionless. m/s2
As shown below, if F = 85.0 N and M = 6.00 kg, what is the magnitude of the acceleration (in m/s2) of the suspended object? All surfaces are frictionless. m/s2
A mass of 0.4 kg hangs motionless from a vertical spring whose length is 1.02 m and whose unstretched length is 0.42 m. Next the mass is pulled down to where the spring has a length of 1.19 m and given an initial speed upwards of 1.7 m/s. What is the maximum length of the spring during the motion that follows? maximum length =
Which graph depicts and object moving in one direction with a constant rate of acceleration (slowing down), then changing direction, and continuing in the opposite direction with a constant rate of acceleration (speeding up)? 1 2 3 4 5
Which graph represents an object moving fast with constant velocity, then moving slow with constant velocity. 1 2 4 5
Which graph depicts and object moving with constant velocity, then slowing down. 1 2 3 4 5
A motorist was moving with a constant velocity higher than the local speed limit. A police officer who was at rest at t = 0 started to chase the motorist with a constant acceleration. The officer caught up with the motorist at t = 10 sec. Which of the following v−t graphs best represents this situation? (a) (b) (c) (d)
Two atoms are connected by a spring-like force with an effective spring constant k. The atoms are squeezed together by a total distance of Δx (distance from equilibrium, L0). What is the total kinetic energy of the two masses as they pass through the equilibrium point? A. 14 kΔx2 B. kΔx2 C. 2 kΔx2 D. 12 kΔx2 E. 0
A small remote-control car with mass 1.60 kg moves at a constant speed of v = 12.0 m/s in a vertical circle inside a hollow metal cylinder that has a radius of 5.00 m (Figure 3). What is the magnitude of the normal force exerted on the car by the walls of the cylinder at A ) point A (at the bottom of the vertical circle) and B) point B (at the top of the vertical circle)? Figure 3
A small remote-controlled car with mass 1.60 kg moves at a constant speed of v = 12.0 m/s in a track formed by a vertical circle inside a hollow metal cylinder that has a radius of 5.00 m. What is the magnitude of the normal force exerted on the car by the walls of the cylinder at (a) point A (bottom of the track) and (b) point B (top of the track)?
A dog running in an open field has components of velocity vx = 2.1 m/s and vy = −2.5 m/s at t1 = 10.0 s. For the time interval from t1 = 10.0 s to t2 = 20.0 s, the average acceleration of the dog has magnitude 0.43 m/s2 and direction 32.0∘ measured from the +x-axis toward the +y-axis. (a) At t2 = 20.0 s, what are the x and y components of the dog's velocity? vx = m/s vy = m/s m/s (b) At t2 = 20.0 s, what are the magnitude and direction of the dog's velocity? magnitude m/s direction ∘ counterclockwise from the +x-axis (c) Sketch the velocity vectors at t1 and t2. Choose File No file chosen How do these two vectors differ?
Disk A has a mass of 2 kg and is sliding forward on the smooth surface with velocity 5 m/s when it strikes a 4-kg disk B, which is sliding towards A at a velocity of 2 m/s with direct central impact. If the coefficient of restitution between the disks is e = 0.6, compute the velocities of A and B just after the collision. Velocity of A and B:
As the drawing illustrates, two disks with masses m1 and m2 are moving horizontally to the right at a speed of v0. They are on an airhockey table, which supports them with an essentially frictionless cushion of air. They move as a unit, with a compressed spring between them, which has a negligible mass. Then the spring is released and allowed to push the disks outward. Consider the situation where disk 1 comes to a momentary halt shortly after the spring is released. Assuming that m1 = 1.0 kg, m2 = 2.2 kg, and v0 = +5.3 m/s, find the velocity of disk 2 at that moment.
In the figure here, a small block is sent through point A with a speed of 6.2 m/s. Its path is without friction until it reaches the section of length L = 13 m, where the coefficient of kinetic friction is 0.75. The indicated heights are h1 = 5.2 m and h2 = 2.9 m. What are the speeds of the block at (a) point B and (b) point C? (c) Does the block reach point D? (d) If so, what is its speed there; if not, how far through the section of friction does it travel?
The sled dog in FIGURE EX7.14 drags sleds A and B across the snow. The coefficient of friction between the sleds and the snow is 0.10. If the tension in rope 1 is 150 N, what is the tension in rope 2 ? FIGURE EX7.14
Problem #2. Block B in the schematic weighs 160.0 N and hangs from 3 strings. Angle D is 76.0 degrees. The system is in equilibrium. The coefficient of static friction between block A and the surface on which it rests is 0.3 and the coefficient of kinetic friction is 0.2 . A. What is the work done by the frictional force (in J)? B. What is the tension on string 2 (in N)? C. Suppose the tension on string 1 is 500 N. What is the minimum weight (in N ) of block A that is required to keep the system in equilibrium?
Figure shows two cases in which a positively charged particle is moving near a bar magnet. What is the direction of the magnetic force in each case?
The uniform solid block in the figure has mass 19.1 kg and edge lengths a = 0.873 m, b = 1.45 m, and c = 0.110 m. Calculate its rotational inertia about an axis through one corner and perpendicular to the large faces. Number Units the tolerance is +/−2%
The uniform solid block in the figure has mass 18.9 kg and edge lengths a = 0.622 m, b = 1.93 m, and c = 0.0999 m. Calculate its rotational inertia about an axis through one corner and perpendicular to the large faces. Number Units the tolerance is +/−2%
A 100 N box is initially at rest on a rough horizontal surface. The coefficient of static friction between the block and the surface is 0.6 and the coefficient of kinetic friction is 0.4 . A man decides to move the box so he applies a steadily increasing horizontal force FApplied on the box to the right as shown. The graph on the left below shows the horizontal force FApplied on the box as it goes from 0 to 80 N as a function of time over 4 seconds. In the graph on the right below, sketch the frictional force exerted on the box by the surface as a function of time. Explain.
The log has a coefficient of static friction of μs = 0.3 with the ground and a weight of 40 lb/ft. If a man can pull on the rope with a maximum force of 80 lb, determine the greatest length 1 of log he can drag
The figure below shows a sketch a box of mass m being pulled to the right at by a force F at an angle θ = 30∘. a) Draw a free-body diagram of forces on the box in the space to the right. Show both horizontal and vertical forces. Include friction. b) Now define a set of x−y axes (show on your fbd) in the usual fashion (horizontal and vertical) c) RESOLVE INTO COMPONENTS any vectors that are not already in the x or y direction. Show and label your components d) Based on your fbd, write two F = ma type equations, one for x and one for y. e) Solve the y equation for the normal force. Put a box around it. f) Solve the x equation for the acceleration α. Put a box around it. g) Plug and chug to get a numbers for the normal force and the acceleration. Use F = 120 N, m = 20 kg, and a frictional force of 34 N. Box your answers.
Ball A(m = 0.5 kg, I = 0.7 MR2) is held at rest against a spring, compressed by a distance x = 40 cm. The ball is released and move along a frictionless surface (H0 = 4 m) until it collides with ball B(m = 0.25 kg, I = 0.5 MR2 ) which is at rest. After the collision, the two balls roll down a track (which has friction!) and leaves the track at a height, H1 = 1 m. Ball B goes to a height of HB = 5 m before it comes to rest and ball A goes a height of HA = 3 m before it stops. Find the spring constant, k, of the spring.
Multiple-Concept Example 7 discusses how problems like this one can be solved. A 4.60−μC charge is moving with a speed of 8.70×104 m/s parallel to a very long, straight wire. The wire is 4.40 cm from the charge and carries a current of 68.0 A. Find the magnitude of the force on the charge. Number Units
Due to a jaw injury, a patient must wear a strap (Figure 1) that produces a net upward force of 5.40 N on his chin. The tension is the same throughout the strap. For help with math skills, you may want to review: Vector Addition Figure 1 of 1 Part A To what tension must the strap be adjusted to provide the necessary upward force? Express your answer in newtons. View Available Hint(s) F = N Submit Previous Answers
A contestant in a winter games event pushes a 47.0 kg block of ice across a frozen lake as shown in the figure below. The coefficient of static friction is 0.1 and the coefficient of kinetic friction is 0.03. (Assume θ = 31∘.) (a) Calculate the minimum force F (in N) he must exert to get the block moving. N (b) What is its acceleration (in m/s2 ) once it starts to move, if that force is maintained? m/s2
A spring with a spring constant of 500 N/m is used to propel a 0.44−kg mass up an inclined plane. The spring is compressed 30 cm from its equilibrium position and launches the mass from rest across a horizontal surface and onto the plane. The plane has a length l = 2 m and is inclined at 32∘. Both the plane and the horizontal surface have a coefficient of kinetic friction with the mass of 0.35 . When the spring is compressed, the mass is at distance d = 1.4 m from the bottom of the plane. (a) What is the speed of the mass as it reaches the bottom of the plane? (b) What is the speed of the mass as it reaches the top of the plane? (c) What is the total work done by friction from the beginning to the end of the mass's motion?
Two professional skaters (Joe and Sue) start their routine by pushing off from a facing, stationary pose as shown in figure (a). The kinetic frictional force acting on their skates can be ignored while they are pushing against each other, however once they separate, the force of kinetic friction eventually brings them to a halt. As shown in figure (b), after the push-off, they move in opposite directions with different speeds. (a) (b) The magnitude of their acceleration is the same, but Sue glides 4 times as far as Joe before coming to rest. Determine the ratio of their masses mS/mJ. mS mJ =
A mass of 8 kg is attached to the end of a spring with a natural length 0.6 m. A force of 128 N is required to maintain the spring stretched to the length of 1 m in the positive x direction beyond the equilibrium point at x = 0. It is stretched to a length of 1 m and then released with initial velocity 0 . Find the position x(t) of the mass at any time t. x(t) =
A mass of 0.5 kg is attached to the end of a spring. To stretch the spring 2 m in the positive x direction beyond its equilibrium position, a force of 144 N must be applied. The mass is then pulled x(0) = 0.8 m from equilibrium position and set in motion with an initial velocity of −12 m/s. Find the position x(t) of the mass at any time t. x(t) =
You promised your younger brother that you would give him a ride on his sled. (Take the positive î direction to be to the right and the positive j^ direction to be upward.) (a) You first pull him with a force F→1 = (53.0ı^ + 23.0 j^) N. If the mass of the sled and boy is 59.0 kg and the coefficient of kinetic friction is 0.046 , what is the acceleration of the sled? Express your answer in vector form. ax = m/s2 (b) After a while, you decide to push him from behind with a force F→2 = (53.0ı^ − 23.0 j^) N. Determine the acceleration of the sled now to see if it will be different from your answer in part (a). Express your answer in vector form. ax = m/s2
How much work (in J) is done by the boy pulling his sister 35 m in a wagon as shown in the figure below? (i) Assume no friction acts on the wagon. (Assume d = 35 m and F = 55 N. Enter a number.) w = J
The sled dog in the figure shown below drags sleds A and B across the snow. The coefficient of friction between the sleds and the snow is 0.10. If the tension in rope 1 is 150 N, what is the tension in rope 2?
Due to a jaw injury, a patient must wear a strap (Figure 1) that produces a net upward force of 4.60 N on his chin. The tension is the same throughout the strap. For help with math skills, you may want to review: Vector Addition Figure 1 of 1 To what tension must the strap be adjusted to provide the necessary upward force? Express your answer in newtons. View Available Hint(s) Hint 1. How to approach the problem What can be said about the sum of the forces acting on the jaw? Start by drawing a sketch of the jaw and the forces acting on it. Choose an appropriate coordinate system, and resolve the vector components accordingly. Use this to calculate the force exerted on each side of the jaw by the strap. F = N
Two blocks are connected by a massless rope as shown below. The mass of the block on the table is 4.9 kg and the hanging mass is 1.9 kg. The table and the pulley are frictionless. (a) Find the acceleration (in m/s2 ) of the system. (Enter the magnitude.) m/s2 (b) Find the tension (in N) in the rope. N (c) Find the speed (in m/s) with which the hanging mass hits the floor if it starts from rest and is initially located 2.1 m from the floor. m/s
In the figure, a tin of anti-oxidants (m1 = 4.3 kg) on a frictionless inclined surface is connected to a tin of corned beef (m2 = 2.9 kg). The pulley is massless and frictionless. An upward force of magnitude F = 6.2 N acts on the corned beef tin, which has a downward acceleration of 5.2 m/s2. What are (a) the tension in the connecting cord and (b) angle β ? (a) Number Units (b) Number Units
A mass of 0.4 kg hangs motionless from a vertical spring whose length is 0.76 m and whose unstretched length is 0.45 m. Next the mass is pulled down to where the spring has a length of 1.05 m and given an initial speed upwards of 1.9 m/s. What is the maximum length of the spring during the motion that follows? maximum length = m
In the figure, what is the magnitude and direction (+ is toward right) of the net force on charge A? (in unit of KN, where K is the electrostatic constant.) On charge B ? (in KN) On charge C ? (in KN)
As shown in the figure below, a uniform beam is supported by a cable at one end and the force of friction at the other end. The cable makes an angle of θ = 30∘, the length of the beam is L = 4.00 m, the coefficient of static friction between the wall and the beam is μs = 0.580, and the weight of the beam is represented by w. Determine the minimum distance x from point A at which an additional weight 2w (twice the weight of the rod) can be hung without causing the rod to slip at point A. x = m
(a) Calculate the de Broglie wavelength (in m) of a 1.40 kg rock thrown with a speed of 4.50 m/s into a pond. m (b) Is this wavelength similar to that of the water waves produced? Explain. Yes, the wavelength of the water waves depends on the medium; they are strictly mechanical waves. No, the wavelength of the water waves depends only on the speed of the rock. No, the wavelength of the water waves depends on the medium; they are strictly mechanical waves. Yes, the wavelength of the water waves depends on the mass and speed of the rock.
You are working in a warehouse monitoring the movement of packages when suddenly you spot one going down a closed ramp with a trailing rope. You decide to jump on the ramp, grab the rope, and bring the 5-kg package to rest before it falls off and gets damaged. Consider the scenario where you grab the rope when the package is 3 -meters from the end of the ramp and has a speed of 2.5 m/s. Let the coefficients of static and kinetic friction be 0.5 and 0.2, respectively, between the package and the ramp. What tension will you need to apply to bring the package to rest when it reaches the bottom of the ramp?
Find the normal strength using the following figure. The mass of the block is 6.0 kg. Two forces acting on a block on a friction-free surface. 1.60 m/s2 1.92 m/s2 1.56 m/s2 1.47 m/s2
A force F→ of magnitude 10 N acts on a uniform massless rod as shown below. The rod is connected to a pivot on the bottom left and is oriented θ = 30∘ above the horizontal. The force is oriented at an angle of ϕ = 10∘ from the vertical. What is the torque about the given pivot point? Drawing is not to scale. The horizontal distance between the pivot and the force is 0.50 m. (Ignore the 0.25 m distance).
Consider an electric dipole where the positive charge, +q, is located on the positive z axis a distance d/2 above the x−y plane, and the negative charge, −q, is located on the negative z axis a distance d/2 below the x−y plane, as shown. If the evaluation point is at a distance which is very large as compared to the separation between the charges, then the form of the expression for the net electric field has a very simplified form in terms of the electric dipole moment (EDM).
The graph below shows the velocity of an object (in ft/sec) as a function of time t (in seconds). Time (sec) Find the total displacement from t = 0 to t = 1: Displacement = feet Find the total displacement from t = 1 to t = 9: Displacement = feet
The electric field in a region is pointed away from the z-axis and the magnitude depends upon the distance s from the axis. The magnitude of the electric field is given as E = α/s where α is a constant. Find the potential difference between points P1 and P2, explicitly stating the path over which you conduct the integration for the line integral.
You have a light spring which obeys Hooke's law. This spring stretches 2.86 cm vertically when a 3.00 kg object is suspended from it. Determine the following. (a) the force constant of the spring (in N/m) N/m (b) the distance (in cm) the spring stretches if you replace the 3.00 kg object with a 1.50 kg object Cm (c) the amount of work (in J) an external agent must do to stretch the spring 7.90 cm from its unstretched position J
(a) Calculate the force (in N) the woman in the figure below exerts to do a push-up at constant speed, taking all data to be known to three digits. (You may need to use torque methods from a later chapter.) m = 53 kg N (b) How much work (in J) does she do if her center of mass rises 0.220 m? J (c) What is her useful power output (in W) if she does 15 push-ups in 1 min? (Should work done lowering her body be included? See the discussion of useful work in Work, Energy, and Power in Humans.) W
A lineman is trying to push a training dummy with a force F1 downward at an angle of θ = 39.15∘. His coach is pushing horizontally against the dummy in the opposite direction, with a force of magnitude F2 = 78.22 N. The dummy has a mass of m = 35.71 kg. The lineman exerts a force F1 = 258.53 N. If the dummy just starts to move in the direction of F1, what is the magnitude of the coefficient of static friction between the dummy and the ground? Retain your answer to two decimal places.
As shown in the figure, three force vectors act on an object. The magnitude of the forces as shown in the figure are F1 = 36 N, F2 = 42 N, and F3 = 23 N. Determine the resultant (net) force acting on the object. 42 N at 90∘ with respect to the +x-axis 101 N at 60∘ with respect to the +x-axis 19.0 N at 82∘ with respect to the +x-axis 60.55 N 82∘ with respect to the +x-axis 23 N at 60∘ with respect to the +x-axis
A thin 2.00 kg box rests on a 6.50 kg board that hangs over the end of a table, as shown in (Figure 1). Figure 1 of 1 30.0 cm 20.0 cm How far can the center of the box be from the end of the table before the board begins to tilt? Express your answer with the appropriate units. x =
You promised your younger brother that you would give him a ride on his sled. You first push him from behind with a force of magnitude F1 directed downward at an angle of 25∘ below the horizontal. After a while you decide to pull him with a force of magnitude F2 directed upward at the same angle above the horizontal. In both cases the sled moves with the same acceleration and friction is negligible. Which of the following statements is true regarding the two forces you used? F1 = F2 F1 > F2 F1 < F2 not enough information
You promised your younger brother that you would give him a ride on his sled. You first pull him with a force F directed upward at an angle of 25∘ to the horizontal. After a while you decide to push him from behind with the same force F directed downward at an angle of 25∘. There is significant friction between the sled and the ice surface. Which of the following statements is true regarding the acceleration of the sled? apull = apush apull > apush apull < apush not enough information