Physics Final
Two blocks of masses 1.0 kg and 2.0 kg, respectively, are pushed by a constant applied force F across a horizontal frictionless table with constant acceleration such that the blocks remain in contact with each other, as shown above. The 1.0 kg block pushes the 2.0 kg block with a force of 2.0 N. The acceleration of the two blocks is
1.0 m/s2
The graph above shows velocity v as a function of time t for a 0.50 kg object traveling along a straight line. The graph has three segments labeled 1, 2, and 3. A rope exerts a constant force of magnitude FT on the object along its direction of motion the whole time. During segment 2 only, a frictional force of magnitude Ff is also exerted on the object. For another identical object initially at rest, no frictional force is exerted during segment 2 (between t = 2 s and t = 4 s). A rope exerts the same constant force of magnitude FT as in the previous scenario. What is the change in the object's kinetic energy during segment 2?
12.0 J
A person applies an impulse of 5.0 kg∙m/s to a box in order to set it in motion. If the person is in contact with the box for 0.25 s, what is the average force exerted by the person on the box?
20.0 N
A distant planet has an acceleration due to gravity of 4 m/s2 near its surface. An object is released from rest from the top of a tall cliff on the planet, and the object lands at the bottom of the cliff in 20 seconds. A second object is then thrown upward from the edge of the same cliff with a speed of 4 m/s. The time it takes the second object to reach the bottom of the cliff is most nearly
21s
Four rods, each of mass M , are pinned at the left end to the horizontal surface of a table and are shown from above in the following figures. Each rod is free to rotate about a pivot at its left end with negligible friction. In each case, forces are exerted on the rod with different magnitudes and in different directions as shown. The rotational inertia of a rod of mass M and length L about the end of the rod is (1/3)ML2 . In which cases do the rods experience equal initial angular accelerations?
2l and 2f/L and 2f sin60
The system shown above is released from rest. If friction is negligible, the acceleration of the 4.0 kg block sliding on the table shown above is most nearly
3.3 m/s^2
In a lab, a block weighing 80 N is attached to a spring scale, and both are pulled to the right on a horizontal surface, as shown above. Friction between the block and the surface is negligible. What is the acceleration of the block when the scale reads 32 N?
4.0 m/s^2
The two blocks of masses M and 2M shown above initially travel at the same speed v but in opposite directions. They collide and stick together. How much mechanical energy is lost to other forms of energy during the collision?
4/3mv^2
A block is projected up a frictionless plane with an initial speed vo. The plane is inclined 30° above the horizontal. What is the approximate acceleration of the block at the instant that it reaches its highest point on the inclined plane?
5 m/s2 down the incline
The graph above represents position x versus time t for an object being acted on by a constant force. The average speed during the interval between 1 s and 2 s is most nearly
6 m/s
The angular momentum of a rigid body rotating around a fixed point as a function of time is shown in the graph. Which of the following statements are true? Select two answers.
Angular Acceleration is Constant/Net Torque Applied is Constant
Two blocks are connected to identical ideal springs and are oscillating on a horizontal frictionless surface. Block A has mass m, and its motion is represented by the graph of position as a function of time shown above on the left. Block B's motion is represented above on the right. Which of the following statements comparing block B to block A is correct?
Because block B has more mass, its acceleration is smaller than that of block A at any given displacement from the equilibrium position.
The figures show a cart moving over the top of a hill (Case 1), moving at the bottom of a dip (Case 2), and moving at the top of a vertical loop (Case 3). In each case, the normal force acting on the car is Fn and the weight of the car is Fg . In which case is it always true that Fn>Fg , and in which case is it always true that Fn<Fg ?
Case 2/Case 1
The position and velocity of a car moving along a straight road are recorded as functions of time, as shown in the graphs above. Which of the following correctly describes the car's speed and acceleration?
Decreasing Speed/Positive Acceleration
A solid metal bar is at rest on a horizontal frictionless surface. It is free to rotate about a vertical axis at the left end. The figures below show forces of different magnitudes that are exerted on the bar at different locations. In which case does the bar's angular speed about the axis increase at the fastest rate?
F to the Right
A cart of mass m rolls past the circular bottom of a hill (point P ). Which of the following statements about the normal force Fn exerted on the cart at point P is correct?
Fn is greater than mg at point P, because the cart is experiencing an upward acceleration.
The incomplete data in the table above were recorded during an experiment in which two carts on a frictionless one-dimensional track collided head-on. What are the magnitudes of the average force F2 exerted on cart 2 and the average acceleration a2 of cart 2 during the collision?
Force Stays the Same/Acceleration is Doubled
A force of constant magnitude F and fixed direction acts on an object of mass m that is initially at rest. If the force acts for a time interval ∆t over a displacement ∆x , what is the magnitude of the resultant change in the linear momentum of the object?
FΔt
A platform is initially rotating on smooth ice with negligible friction, as shown at left in the figure. A stationary disk is dropped directly onto the center of the platform. A short time later, the disk and platform rotate together at the same angular velocity, as shown at right in the figure. How does the angular momentum of only the platform change, if at all, after the disk drops? What is a justification for your answer?
It decreases. The top disk exerts a torque on the platform.
The toy car shown in the figure above enters the vertical circular loop with an initial velocity and moves completely around the loop without friction. If the car has no means of self-propulsion, which of the following is true of the car's acceleration at the instant it is at point P ?
It has components both downward and toward the center of the circle.
A system consists of a disk rotating on a frictionless axle and a piece of clay moving toward it, as shown in the figure above. The outside edge of the disk is moving at a linear speed v, and the clay is moving at speed v/2. The clay sticks to the outside edge of the disk. How does the angular momentum of the system after the clay sticks compare to the angular momentum of the system before the clay sticks, and what is an explanation for the comparison?
It is the same because there is no external torque acting on the system.
How does an air mattress protect a stunt person landing on the ground after a stunt?
It lengthens the stopping time of the stunt person and reduces the force applied during the landing.
a horizontal table. The disk collides elastically with a uniform rod of length ℓ that is at rest and free to pivot about one end, as shown in Figure 1 above. The disk rebounds to the left with speed vf , and the rod rotates with friction and stops at a final angle θf from its initial position, as shown in Figure 2. Immediately after the collision, the rod has angular speed ω , and the rod comes to rest a time Δt after the collision. If the rotational inertia of the rod about the pivot is I , the average torque exerted on the rod by friction while the rod is coming to rest is
Iw/t
A simple pendulum consisting of a small object of mass m attached to a string of length l has a period T. A pendulum with which of the following combinations of object mass and string length will also have period T ?
L string length
A railroad car of mass m is moving with speed u when it collides with and connects to a second railroad car of mass 3m, initially at rest, as shown above. How do the speed and kinetic energy of the connected cars compare to those of the single car of mass m before the collision?
Less Speed/Less KE
The figure above shows a uniform beam of length L and mass M that hangs horizontally and is attached to a vertical wall. A block of mass M is suspended from the far end of the beam by a cable. A support cable runs from the wall to the outer edge of the beam. Both cables are of negligible mass. The wall exerts a force FW on the left end of the beam. For which of the following actions is the magnitude of the vertical component of FW smallest?
Moving both the support cable and the block to the center of the beam
An asteroid orbits the Sun in a highly elliptical orbit. As the asteroid gets closer to the Sun, how are the total mechanical energy and the gravitational potential energy of the asteroid-Sun system changing, if at all?
TME Doesn't Change/GPE Decreasing
An object attached to one end of a string moves in a circle at constant speed. Which of the following is correct?
The object is accelerating as it moves.
A person holds a book at rest a few feet above a table. The person then lowers the book at a slow constant speed and places it on the table. Which of the following accurately describes the change in the total mechanical energy of the Earth-book system?
The total mechanical energy decreases, because the person does negative work on the book by exerting a force on the book in the direction opposite to its displacement.
A dart and a rubber sphere are suspended from the same point by light strings. When the dart is released from the position shown above, it swings downward until its tip strikes the sphere. The dart can have different tips attached. Tip A will stick into the rubber sphere upon impact. Tip B will bounce inelastically off the sphere. Tip C will bounce elastically off the sphere. For which tip, if any, will the sphere swing to the greatest maximum angle θ ?
Tip C
a horizontal table. The disk collides elastically with a uniform rod of length ℓ that is at rest and free to pivot about one end, as shown in Figure 1 above. The disk rebounds to the left with speed vf , and the rod rotates with friction and stops at a final angle θf from its initial position, as shown in Figure 2. Which of the following describes the direction of the forces exerted by the disk and rod on each other during the collision?
To the left/To the right
A bicycle wheel of known rotational inertia is free to rotate about its central axis. With the wheel initially at rest, a student wraps a string around the wheel and pulls the string with a spring scale, causing the wheel to rotate. The student records the tension in the string and the time for which the string was pulled. Without measuring the wheel's final angular speed, can the student find the magnitude of the wheel's final angular momentum, and what is a correct explanation?
Yes. The student also needs to measure the wheel's radius to calculate the torque exerted on the wheel.
An artificial satellite orbits Earth at a speed of 7800 m/s and a height of 200 km above Earth's surface. The satellite experiences an acceleration due to gravity of
less than 9.8 m/s2 but greater than zero
Two identical objects, X and Y, move toward each other at different speeds on a horizontal surface with negligible friction, as shown in the top figure. The objects then collide elastically and move away from each other. The kinetic energy of object X as a function of time is shown in the graph. Which of the following is true of the speed vY of object Y?
vY after the collision is greater than it was before the collision.
The graph above shows velocity v as a function of time t for a 0.50 kg object traveling along a straight line. The graph has three segments labeled 1, 2, and 3. A rope exerts a constant force of magnitude FT on the object along its direction of motion the whole time. During segment 2 only, a frictional force of magnitude Ff is also exerted on the object.
x3 > x2 > x1 > 0
Two particles collide and stick together. If no external forces act on the two particles, which of the following is correct for the change in total momentum Δp and the change in total kinetic energy ΔK of the two particles?
Δp = 0; ΔK< 0
