AP Physics 1 Forces and Newton's Law Practice

33) The figure shows a block of mass m resting on a 20° slope. The block has coefficients of friction !s = 0.64 and !k = 0.54 with the surface of the slope. It is connected using a very light string over an ideal pulley to a hanging block of mass 2.0 kg. The string above the slope pulls parallel to the surface. What is the minimum mass m so the system will remain at rest when it is released from rest?

A) 3.6 kg B) 1.3 kg C) 2.1 kg D) 3.3 kg

30) A 15-kg block is on a frictionless ramp that is inclined at 20° above the horizontal. It is connected by a very light string over an ideal pulley at the top edge of the ramp to a hanging 19-kg block, as shown in the figure. The string pulls on the 15-kg block parallel to the surface of the ramp. Find the magnitude of the acceleration of the 19-kg block after the system is gently released? A) 4.0 m/s2 B) 4.5 m/s2 C) 4.2 m/s2 D) 3.8 m/s2

A) 4.0 m/s2

9) A person is using a rope to lower a 5.0-N bucket into a well with a constant speed of 2.0 m/s. What is the magnitude of the force exerted by the rope on the bucket? A) 5.0 N B) 2.0 N C) 10 N D) 49 N

A) 5.0 N

2) A 1200-kg car is pulling a 500-kg trailer along level ground. Friction of the road on the trailer is negligible. The car accelerates with an acceleration of 1.3 m/s2. What is the force exerted by the car on the trailer? A) 650 N B) 600 N C) 750 N D) 700 N

A) 650N

8) A small car and a large SUV are at a stoplight. The car has a mass equal to half that of the SUV, and the SUV can produce a maximum accelerating force equal to twice that of the car. When the light turns green, both drivers push their accelerators to the floor at the same time. Which vehicle pulls ahead of the other vehicle after a few seconds? A) It is a tie. B) The car pulls ahead. C) The SUV pulls ahead.

A) It is a tie.

1) You are in a train traveling on a horizontal track and notice that a piece of luggage starts to slide directly toward the front of the train. From this observation, you can conclude that this train is A) slowing down. B) speeding up and changing direction. C) changing direction. D) slowing down and changing direction.

A) Slowing Down

22) Two boxes are connected to each other by a string as shown in the figure. The 10-N box slides without friction on the horizontal table surface. The pulley is ideal and the string has negligible mass. What is true about the tensionT in the string? A) T < 30 N B) T > 30 N C) T = 60 N D) T = 30 N

A) T< 30 N

7) You push on box G that is next to box H, causing both boxes to slide along the floor, as shown in the figure. The reaction force to your push is A) the push of box G against you. B) the acceleration of box G. C) the push of box H on box G. D) the push of box G on box H

A) The push of box G against you.

20) A push of magnitude P acts on a box of weightW as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to A) W + P sin θ. B) W+P cos θ. C) W+P. D) W- P sin θ.

A) W + P sin θ.

32) In the figure, block A has a mass of 3.00 kg. It rests on a smooth horizontal table and is connected by a very light horizontal string over an ideal pulley to block B, which has a mass of 2.00 kg. When block B is gently released from rest, how long does it take block B to travel 80.0 cm? A) 0.404 s B) 0.639 s C) 0.494 s D) 0.935 s

B) 0.639 s

17) A truck is using a hook to tow a car whose mass is one quarter that of the truck. If the force exerted by the truck on the car is 6000 N, then the force exerted by the car on the truck is A) 6000 N. B) 1500 N. C) 24000 N. D) 12000 N.

B) 1500 N

29) The figure shows a 100-kg block being released from rest from a height of 1.0 m. It then takes 0.53 s for it to reach the floor. What is the mass m of the block on the left? There is no friction or mass in the pulley, and the connecting rope is very light. A) 14 kg B) 16 kg C) 11 kg D) 13 kg

B) 16 kg

11) A person who normally weighs 700 N is riding in a rather swift elevator that is moving at a constant speed of 9.8 m/s. If this person is standing on a bathroom scale inside the elevator, what would the scale read? A) less than 700 N B) 700 N C) more than 700 N D) It could be more or less than 700 N, depending on whether the elevator is going up or down.

B) 700N

31) You push downward on a trunk at an angle 25° below the horizontal with a force of 750 N. If the trunk is on a flat surface and the coefficient of static friction between the surface and the trunk is 0.61, what is the most massive trunk you will be able to move? A) 112 kg B) 81 kg C) 93 kg D) 73 kg

B) 81 kg

16) A 20-ton truck collides with a 1500-lb car. Which of the following statements must be true? A) The car did not slow down during the collision, but the truck did. B) During the collision, the force on the truck is equal to the force on the car. C) During the collision, the force on the truck is greater then the force on the car. D) During the collision, the force on the truck is smaller than the force on the car.

B) During the collision, the force on the truck is equal to the force on the car.

18) A golf club hits a golf ball with a force of 2400 N, sending the ball into the air. The force exerted on the club by the ball must be less than 2400 N or else the ball would not have moved forward. A) True B) False C) The answer depends on whether the golfer followed through with the swing.

B) False

14) An object of mass m rests on a flat table. The earth pulls on this object with a force of magnitude mg. What is the reaction force to this pull? A) The table pushing up on the object with force mg. B) The object pulling upward on the Earth with force mg. C) The object pushing down on the table with force mg. D) The table pulling upward on the Earth with force mg

B) The object pulling upward on the Earth with force mg.

23) Two boxes, A and B, are connected by a horizontal string S on a horizontal floor. A very light wire pulls horizontally on box B, as shown in the figure, with a force of 100 N. The reaction force to this pull is A) the force that box A exerts on box B. B) the pull of box B on the wire. C) the pull that string S exerts on box A. D) the pull that box B exerts on string S.

B) the pull of box B on the wire.

25) A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the hill exerts on the sled parallel to the surface of the hill? A) 120 N B) 200 N C) 0 N D) 160 N

C) 0 N

13) An object of weight W is in freefall close to the surface of Earth. The magnitude of the force that the object exerts on Earth is A) less than W. B) cannot be determined without knowing the relative masses of the object and the earth. C) equal to W. D) greater than W.

C) Equal to W

12) A horse pulls a cart with force F . As a result of this force the cart accelerates with constant acceleration. The magnitude of the force that the cart exerts on the horse A) is zero newtons. B) greater than the magnitude of F . C) equal to the magnitude of F . D) less than the magnitude of F .

C) Equal to the magnitude of F.

15) An object is moving with constant non-zero velocity. Which of the following statements about it must be true? A) A constant force is being applied to it in the direction of motion. B) Its acceleration is in the same direction as it velocity. C) The net force on the object is zero. D) A constant force is being applied to it perpendicular to the direction of motion

C) The net force on the object is zero.

6) A 45.0-kg person steps on a scale in an elevator. The scale reads 460 N. What is the magnitude of the acceleration of the elevator? A) 0.206 m/s2 B) 46.9 m/s2 C) 4.91 m/s2 D) 0.422 m/s2

D) 0.422 m/s2

5) A block is on a frictionless table, on earth. The block accelerates at 5.3 m/s2 when a 10 N horizontal force is applied to it. The block and table are set up on the Moon where the acceleration due to gravity is 1.62 m/s2. A horizontal force of 5 N is now applied to the block when it is on the Moon. The acceleration imparted to the block by this force is closest to A) 3.2 m/s2. B) 3.4 m/s2. C) 2.9 m/s2. D) 2.7 m/s2

D) 2.7 m/s2

28) A 400-kg box is lifted vertically upward with constant velocity by means of two cables pulling at 40.0° on either side of the vertical direction. What is the tension in each cable? A) 231 N B) 800 N C) 3920 N D) 2560 N

D) 2560 N

10) A 75-N box rests on a perfectly smooth horizontal surface. The minimum force need to start the box moving is A) 7.5 N. B) 75 N. C) 750 N. D) any horizontal force greater than zero.

D) Any Horizontal force greater than zero.

27) A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about normal force F on the block due to the ramp? A) F > mg cos θ B) F > mg sinθ C) F = mg sin θ D) F = mg cos θ

D) F = mg cos θ

3) A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point A) perpendicular to the ramp. B) down the ramp. C) up the ramp. D) None of the above choices is correct.

D) None of the above choices are correct

4) Bill and his daughter Susan are both standing on identical skateboards (with really good frictionless ball bearings), initially at rest. Bill weighs three times as much as Susan. Bill pushes horizontally on Susan's back, causing Susan to start moving away from Bill. Just after Bill stops pushing, A) Susan and Bill are moving away from each other, and Susan's speed is one-third that of Bill. B) Susan is moving away from Bill, and Bill is stationary. C) Susan and Bill are moving away from each other, with equal speeds. D) Susan and Bill are moving away from each other, and Susan's speed is three times that of Bill.

D) Susan and Bill are moving away from each other, and Susan's speed is three times that of Bill.

26) Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance. Which one of the following statements about these objects is correct? A) It takes the lighter object 5 times longer to reach the bottom of the ramp than the heavier. B) It takes the lighter object 10 times longer to reach the bottom of the ramp than the heavier. C) It takes the heavier object 10 times longer to reach the bottom of the ramp than the lighter. D) The two objects reach the bottom of the ramp at exactly the same time.

D) The two objects reach the bottom of the ramp at exactly the same time.