Physics

The inclined plane in the figure above has two sections of equal length and different roughness. The dashed line shows where section 1 ends and section 2 begins. A block of mass M is placed at different locations on the incline. The coefficients of kinetic and static friction between the block and each section are shown in the table below. 67. If the block is sliding up section 2, what is the magnitude of the force of friction that is exerted on the block by the incline? (A) 2 μk Mg cos θ (B) 2 μk Mg tan θ (C) Mg sin θ (D) Mg / tan θ

(A) 2 μk Mg cos θ

73. Object A of mass 2kg is gravitationally attracted to object B of mass 2kg as the two objects float in space. Frictional forces are negligible. The gravitational forces of attraction between the two objects are shown in the table above. Which of these claims about the motion of the center of mass of the two-object system is true? (A) The center of mass will not accelerate. (B) The center of mass will accelerate at .675 x 10^-10 m/s2 (C) The center of mass will accelerate at 5.4 x 10^-10 m/s2 (D) The center of mass will accelerate at 2.7 x 10^-10 m/s2

(A) The center of mass will not accelerate.

17. One end of a string is attached to an object of mass M, and the other end of the string is secured so that the object is at rest as it hangs from the string. When the object is raised to a height above its lowest point and released from rest, the object undergoes simple harmonic motion. Three possible positions of the pendulum X,Y, and Z , are shown in the figure. Which of the following claims is correct regarding the mechanical energy of the pendulum? (A) The magnitude of the change in gravitational potential energy from point X to point Y is the same as from point Y to point Z. (B) The pendulum has half of its maximum speed whenever it is at a vertical position that is halfway between point X and point Y. (C) A pendulum with twice the mass will have twice the speed at the lowest point along the pendulum's arc when compared to the pendulum that is shown in the figure. (D) A pendulum that is released at an angular amplitude that is twice what is shown in the figure will have the same total mechanical energy as the pendulum shown in the figure.

(A) The magnitude of the change in gravitational potential energy from point X to point Y is the same as from point Y to point Z.

A student wants to determine the coefficient of static friction μ between a block of wood and an adjustable inclined plane. Of the following, the minimum additional equipment the student needs to determine a value for μ is (A) protractor only (B) timer only (C) protractor and timer (D) meterstick and timer (E) meterstick and string

(A) protractor only

19. A 1.0 kg block is attached to an unstretched spring of spring constant 50 N/m and released from rest from the position shown in Figure 1 above. The block oscillates for a while and eventually stops moving 0.20 m below its starting point, as shown in Figure 2. What is the change in potential energy of the block-spring-Earth system between Figure 1 and Figure 2 ? (A) −1.0 J (B) 0 J (C) 1.0 J (D) 3.0 J

(A) −1.0 J

18. An object with mass m is suspended at rest from a spring with a spring constant of 200 N/m . The length of the spring is 5.0 cm longer than its unstretched length L, as shown above. A person then exerts a force on the object and stretches the spring an additional 5.0 cm. What is the total energy stored in the spring at the new stretched length? (A) 0.25 J (B) 1.0 J (C) 10 J (D) 20 J

(B) 1.0 J

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? (A) Zero (B) 5 m/s2 down the incline (C) 10 m/s2 down the incline (D) 10 m/s2 up the incline (E) It cannot be calculated without knowing the value of vo

(B) 5 m/s2 down the incline

91. A cart is moving on a level track in the positive x-direction. A force acting parallel to the x-axis is exerted on the cart. The graph above shows the net force exerted on the cart as a function of displacement. As the cart travels from x = 0 m to x = 4 m , what is the net change in the kinetic energy of the cart? (A) An increase of 20 J (B) An increase of 10 J (C) A decrease of 20 J (D) A decrease of 10 J

(B) An increase of 10 J

3. A block of mass 2 kg on a horizontal surface is attached to a horizontal spring of negligible mass and spring constant 100 N/m . The other end of the spring is attached to a wall, and there is negligible friction between the block and the horizontal surface. When the spring is unstretched, the block is located at x=0. The block is then pulled to x=.5m and released from rest so that the block-spring system oscillates between x= -.5m and x=.5m, as shown in the figure. Which of the following predictions is correct regarding the energy of the system? (A) If the mass of the block is changed to .5kg and all other quantities are held constant, the maximum kinetic energy of the system will be half of the value from the original situation. (B) If the spring is changed so that its spring constant is 200 N/m and all other quantities are held constant, the maximum kinetic energy of the system will be twice the value from the original situation. (C) If the block is pulled to x=2m and released from rest and all other quantities are held constant, the maximum kinetic energy of the system will be four times the value from the original situation. (D) If the mass of the block is changed to 1kg and the spring is changed to so that its spring constant is 50 N/m, the maximum kinetic energy of the system will be the same as the value from the original situation.

(B) If the spring is changed so that its spring constant is 200 N/m and all other quantities are held constant, the maximum kinetic energy of the system will be twice the value from the original situation.

A vehicle lands on Mars and explores its surface. The average gravitational field on the surface of Mars is 3.7 N kg . The weight of the vehicle is defined as the gravitational force exerted on it. Which of the following statements are true about the vehicle's weight? Select two answers. (A) The vehicle's weight was constant until it reached the surface of Mars. (B) The vehicle's weight increased while it was descending to the surface of Mars. (C) The vehicle's weight always equals the normal force exerted by Mars on the vehicle while it is landing. (D) The vehicle weighs less on the surface of Mars than on the surface of Earth.

(B) The vehicle's weight increased while it was descending to the surface of Mars. (D) The vehicle weighs less on the surface of Mars than on the surface of Earth.

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? (A) Total Mechanical Energy: not changing, Gravitational Potential Energy Not changing (B) Total Mechanical Energy: not changing, Gravitational Potential Energy: Decreasing (C) Total Mechanical Energy: increasing, Gravitational Potential Energy Not changing (D) Total Mechanical Energy: increasing, Gravitational Potential Energy Decreasing

(B) Total Mechanical Energy: not changing, Gravitational Potential Energy: Decreasing

The inclined plane in the figure above has two sections of equal length and different roughness. The dashed line shows where section 1 ends and section 2 begins. A block of mass M is placed at different locations on the incline. The coefficients of kinetic and static friction between the block and each section are shown in the table below. 68. If the block is at rest on section 1 of the incline, what is the magnitude of the force of static friction exerted on the block by the incline? (A) μs1Mgcosθ (B) μs1Mgtanθ (C) Mg sin θ (D) Mg / tan θ

(C) Mg sin θ

A book is at rest on the top of a table. A student makes the following claim: "An attractive electromagnetic force is exerted on the book from the table, and this force can also be classified as the normal force." Which of the following statements correctly justifies the student's claim? (A) The claim is correct because the charged particles of the table exert a downward attractive force on the charged particles of the book. (B) The claim is correct because the charged particles of the table exert a downward repulsive force on the charged particles of the book. (C) The claim is incorrect because the charged particles of the table exert an upward repulsive force on the charged particles of the book. (D) The claim is incorrect because the charged particles of the table exert an upward attractive force on the charged particles of the book.

(C) The claim is incorrect because the charged particles of the table exert an upward repulsive force on the charged particles of the book.

87. An inclined track is secured to a table. The height of the highest point of the track above the tabletop is h1 . The height from the tabletop to the floor is h2 . A block of mass M is released from rest and slides down the track such that all frictional forces are considered to be negligible. The block leaves the track horizontally and strikes the ground at a distance D from the edge of the track as shown. Which of the following statements is correct about the scenario? Select two answers. (A) If the block is released from a height 2h1 , the block will land at a distance 2D away from the end of the track. (B) If the block's mass is increased to 2M, the block will land at a distance 2D away from the edge of the track. (C) The total mechanical energy of the system containing only the block increases from the moment of release to the moment it strikes the ground. (D) The total mechanical energy of the block-Earth system remains constant.

(C) The total mechanical energy of the system containing only the block increases from the moment of release to the moment it strikes the ground. (D) The total mechanical energy of the block-Earth system remains constant.

98. A student is asked to move a box from ground level to the top of a loading dock platform, as shown in the figures above. In Figure 1, the student pushes the box up an incline with negligible friction. In Figure 2, the student lifts the box straight up from ground level to the loading dock platform. In which case does the student do more work on the box, and why? (A) Lifting the box straight up, because it requires a larger applied force to lift it straight up (B) Pushing the box up the incline, because the force is applied for a longer distance (C) Lifting the box straight up, because the incline acts as a simple machine and reduces the force required (D) Neither method, because the work is the same in both cases, since using the ramp decreases the force by the same factor that it increases the distance

(D) Neither method, because the work is the same in both cases, since using the ramp decreases the force by the same factor that it increases the distance

In Figure 1, cart Y is connected to cart X by a tight string and is also connected to the hanging block of mass M0 by a light string that passes over a pulley. Figure 2 shows a system that is identical except for one change: cart Y and X are connected by a spring at its equilibrium length. Both systems are released from rest. Is the hanging block's acceleration as a function of time the same in both systems, and why or why not? (A) Yes, because the net external force exerted on both systems is the same. (B) Yes, because the tension in the string connecting the block to cart Y is determined by the masses of cart Y and the block. (C) No, because the net external force exerted on each system is different. (D) No, because the tension in the string connected to the block is constant in one system but not in the other

(D) No, because the tension in the string connected to the block is constant in one system but not in the other

2.A pendulum consisting of a sphere suspended from a light string is oscillating with a small angle with respect to the vertical. The sphere is then replaced with a new sphere of the same size but greater density and is set into oscillation with the same angle. How do the period, maximum kinetic energy, and maximum acceleration of the new pendulum compare to those of the original pendulum? (A) Period: larger Maximum Kinetic Energy: larger Maximum Acceleration: Smaller (B) Period: Smaller Maximum Kinetic Energy: Larger Maximum Acceleration: Smaller (C) Period: the same Maximum Kinetic Energy: the same Maximum Acceleration: The same (D) Period: the same Maximum Kinetic Energy: larger Maximum Acceleration: the same

(D) Period: the same Maximum Kinetic Energy: larger Maximum Acceleration: the same

55. A small cart is rolling freely on an inclined ramp with a constant acceleration of 0.50 m/s2 in the -x direction. At time t = 0, the cart has a velocity of 2.0 m/s in the +x-direction. If the cart never leaves the ramp, which of the following statements correctly describes the motion of the cart at a time t > 5 s? (A) The cart is traveling in the +x-direction and is slowing down. (B) The cart is traveling in the +x-direction and is speeding up. (C) The cart is traveling in the -x-direction and is slowing down. (D) The cart is traveling in the -x-direction and is speeding up.

(D) The cart is traveling in the -x-direction and is speeding up.

83. An amusement park ride has two identical carriages that revolve around the center of the ride's axle, as shown in the figure. Both carts travel at a constant tangential speed at all points along the circular path. At what position is the total mechanical energy of the cart-cart-Earth system at its maximum value? Answers r pictures

(D) The total energy of the Earth-Ferris wheel ride is constant

90. A 4kg block is pushed up an incline that makes a 30 degree angle with the horizontal, as shown in the figure. Once the block is pushed a distance of d=5 m up the incline, the block remains at rest. What is the approximate change in the gravitational potential energy of the block-Earth system when the block is held at rest compared to its original location at the bottom of the incline? a. 0J b. 100J c. 100 square root 3 J d. 200 J

B. 100 J

A potato falling vertically downward is struck by a dart that is traveling vertically upward, as shown above. The dart and potato then collide, stick together, and continue moving after the collision. Consider the dart-potato system. Which of the following graphs best represents the speed v of the center-of-mass of the dart-potato system, as a function of time t, before, during, and after the collision? All answers are graphs and no I'm not putting the pictures in dumb but (Q54)

D

Two students need to move two identical boxes of mass M0 across a room where friction between the floor and the boxes cannot be neglected. One student moves the first box by pushing with a force of magnitude F0 at an angle theta from the horizontal, as shown in the figure for scenario 1. The other student moves the second box by pulling with a force of magnitude F0 at the same angle theta from the horizontal, as shown in the figure for scenario 2. Which of the following is a correct expression for the acceleration of the box in scenario 2 ?

a (look it up in the packet its 43 but the answer is mad long and complicated and i cant copy paste it)

Two identical cars, car 1 and car 2, are moving in opposite directions on a straight road. The position of each car as a function of time is represented in the graph. What is the speed of the center of mass of the two-car system? a) 0 b) 10 m/s c) 20 m/s d) 40 m/s

a) 0

1. A block of mass .5kg on a horizontal surface is attached to a horizontal spring of negligible mass and spring constant 50 N/m. The other end of the spring is attached to a wall, and there is negligible friction between the block and the horizontal surface. When the spring is unstretched, the block is located at x=0 . The block is then pulled to x=.3m and released from rest so that the block-spring system oscillates between x=-.3m and .3m. What is the magnitude of the acceleration of the block and the direction of the net force exerted on the block when it is located at x=.3m? not putting in table values

b) Magnitude of acceleration: 30 m/s2 Direction of Net Force: -

On another planet, a ball is in free fall after being released from rest at time . A graph of the height of the ball above the planet's surface as a function of time is shown. The acceleration due to gravity on the planet is most nearly a. 8 m/s2 b. 16 m/s2 c. 20 m/s2 d. 40 m/s2

b. 16 m/s2

82. A 6kg sled starts from rest at the top of a hill and slides down the hill, as shown above. As the sled passes through a point that is 30m vertically below its starting point, it has a speed of 20 m/s . How much mechanical energy was dissipated by frictional forces during the interval shown? a. 0J b. 600J c. 1200J d. 1800J

b. 600J

A ball is released from rest from the twentieth floor of a building. After 1s , the ball has fallen one floor such that it is directly outside the nineteenth- floor window. The floors are evenly spaced. Assume air resistance is negligible. What is the number of floors the ball would fall in 3s after it is released from the twentieth floor? (A) 3 floors or less (B) 4 to 6floors (C) 7 to 10 floors (D) 11 floors or more

c) 7-10 floors

A car initially at rest accelerates at 10 m/s2. The car's speed after it has traveled 25 meters is most nearly a. 0 m/s b. 10 m/s c. 22 m/s d. 25 m/s

c. 22 m/s

An object of mass 10kg is released from rest above the surface of a planet such that the object's speed as a function of time is shown by the graph above. The force due to gravity exerted on the object is most nearly a. 3.5 N b. 7 N c. 35 N d. 70 N

c. 35 N

At which of the following times do the two objects have the same velocity? (based on a graph) a. ta b. tb c. tc d. td

c. tc

88. A block slides down an inclined plane whose roughness varies. Only during time interval 1 does the block slide with negligible friction. The coefficient of kinetic friction during time interval 3 is twice the coefficient of kinetic friction during time interval 2. The graph shows the block's velocity as a function of time. The table lists the mechanical energy dissipated due to friction over the different time intervals. Which of the following claims is true? not typing out answer choices weird equations love

c. |W3|>|W2|>|W4|

97. A block on a horizontal surface is placed in contact with a light spring with spring constant K , as shown in Figure 1. When the block is moved to the left so that the spring is compressed a distance d from its equilibrium length, the potential energy stored in the spring-block system is Em . When a second block of mass 2m is placed on the same surface and the spring is compressed a distance 2D, as shown in Figure 2, how much potential energy is stored in the spring compared to the original potential energy Em ? All frictional forces are considered to be negligible. a. (1/2) Em b. Em c. 2Em d. 4Em

d. 4Em

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 (A) 2 m/s (B) 4 m/s (C) 5 m/s (D) 6 m/s (E) 8 m/s

d. 6 m/s

81. Two blocks of masses m and M are suspended as shown above by strings of negligible mass. If a person holding the upper string lowers the blocks so that they have a constant downward acceleration a, the tension in the string at point P is a. (M+m)g-ma b. (M+m)g-Ma c. Mg-(M+m)a d. Mg e. M(g-a)

e. M(g-a)

Balls 1 and 2 are each thrown horizontally from the same height above level ground, but ball 2 has a greater initial velocity after leaving the thrower's hand. If air resistance is negligible, how do the accelerations of the balls and the times it takes them to hit the ground compare? a. acceleration: greater for ball 2 Time to hit ground: greater for ball 2 b. acceleration: greater for ball 2 time to hit ground: = c. acceleration: = time to hit ground: greater for ball 2 d. acceleration: = time to hit ground: less for ball 2 e. acceleration: = time to hit the ground: =

e. acceleration: = time to hit the ground: =