Chapter 4 Multiple Choice Questions

1.  Which of Newton's laws best explains why motorists should buckle-up?

 

     A) the first law

     B) the second law

     C) the third law

     D) the law of gravitation

 

2.  A rocket moves through empty space in a straight line with constant speed.  It is far from the

     gravitational effect of any star or planet.  Under these conditions, the force that must be applied to

     the rocket in order to sustain its motion is

 

     A) equal to its weight.

     B) equal to its mass.

     C) dependent on how fast it is moving.

     D) zero.

 

3.  You are standing in a moving bus, facing forward, and you suddenly fall forward as the bus comes

     to an immediate stop.  What force caused you to fall forward?

 

     A) gravity

     B) normal force due to your contact with the floor of the bus

     C) force due to friction between you and the floor of the bus

     D) There is not a force leading to your fall.

 

4.  A constant net force acts on an object.  Describe the motion of the object.

 

     A) constant acceleration

     B) constant speed

     C) constant velocity

     D) increasing acceleration

 

5.  A net force F accelerates a mass m with an acceleration a.  If the same net force is applied to

    mass 2m, then the acceleration will be

 

     A) 4a.

     B) 2a.

     C) a/2.

     D) a/4.

 

6.  If you blow up a balloon, and then release it, the balloon will fly away.  This is an illustration of

 

     A) Newton's first law.

     B) Newton's second law.

     C) Newton's third law.

     D) Galileo's law of inertia.

 

7.  A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car.  Since a lot of

     damage is done on the car

 

     A) the force on the truck is greater than the force on the car.

     B) the force on the truck is equal to the force on the car.

     C) the force on the truck is smaller than the force on the car.

     D) the truck did not slow down during the collision.

 

8.  A golf club hits a golf ball with a force of 2400 N.  The golf ball hits the club with a force

 

     A) slightly less than 2400 N.

     B) exactly 2400 N.

     C) slightly more than 2400 N.

     D) close to 0 N.

 

9. Mass and weight

 

      A) both measure the same thing.

      B) are exactly equal.

      C) are two different quantities.

      D) are both measured in kilograms.

 

10. A stone is thrown straight up.  At the top of its path, the net force acting on it is

 

      A) greater than its weight.

      B) greater than zero, but less than its weight.

      C) instantaneously equal to zero.

      D) equal to its weight.

 

11. A 20-N weight and a 5.0-N weight are dropped simultaneously from the same height.  Ignore air

      resistance.  Compare their accelerations.

 

      A) The 20 N weight accelerates faster because it is heavier.

      B) The 20 N weight accelerates faster because it has more inertia.

      C) The 5.0 N weight accelerates faster because it has a smaller mass.

      D) They both accelerate at the same rate because they have the same weight to mass ratio.

 

12. An object of mass m is hanging by a string from the ceiling of an elevator.  The elevator is moving

      up at constant speed.  What is the tension in the string?

 

      A) less than mg

      B) exactly mg

      C) greater than mg

      D) cannot be determined without knowing the speed

 

13. A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal.  The

      normal reaction force exerted by the plane on the block is

 

      A) Mg.

      B) Mg sin θ.

      C) Mg cos θ.

      D) zero, since the plane is frictionless.

 

14. A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal.  The

      gravitational force is directed  

 

      A) parallel to the plane in the same direction as the movement of the block.

      B) parallel to the plane in the opposite direction as the movement of the block

      C) perpendicular to the plane.

      D) toward the center of the Earth.

 

15. Two toy cars (16 kg and 2.0 kg) are released simultaneously on an inclined plane that makes an

      angle of 30° with the horizontal.  Make a statement which best describes their acceleration after

      being released.

 

      A) The 16-kg car accelerates 8 times faster than the 2.0-kg car.

      B) The 2.0-kg car accelerates 8 times faster than the 16-kg car.

      C) Both cars accelerate at the same rate.

      D) none of the above

 

16. An object sits on a frictionless surface.  A 16-N force is applied to the object, and it accelerates at

      2.0 m/s2.  What is the mass of the object?

 

      A) 4.0 kg

      B) 8.0 kg

      C) 32 kg

      D) 78 N

 

17. Starting from rest, a 4.0-kg body reaches a speed of 8.0 m/s in 2.0 s.  What is the net force acting

      on the body?

 

      A) 4.0 N

      B) 8.0 N

      C) 16 N

      D) 32 N

 

18. Sue and Sean are having a tug-of-war by pulling on opposite ends of a 5.0-kg rope.  Sue pulls

      with a 15-N force.  What is Sean's force if the rope accelerates toward Sue at 2.0 m/s2?

 

      A) 3.0 N

      B) 5.0 N

      C) 25 N

      D) 50 N

 

19. A traffic light of weight 100 N is supported by       two ropes as shown in the figure on the right.       What are the tensions in the ropes?         A) 50 N       B) 63 N       C) 66 N       D) 83 N
20. Two boxes of masses m and 2m are in       contact with each other on a frictionless       surface.  (See above figure. What is the       acceleration of the more massive box?         A) F/m       B) F/(2m)       C) F/(3m)       D) F/(4m)

 

21. A 10-kg box sitting on a horizontal surface is pulled by a 5.0-N force.  A 3.0-N friction force retards

      the motion.  What is the acceleration of the object?

 

      A) 0.20 m/s2 

      B) 0.30 m/s2 

      C) 0.50 m/s2 

      D) 5.0 m/s2 

 

22. A horizontal force of 5.0 N accelerates a 4.0-kg mass, from rest, at a rate of 0.50 m/s2 in the

      positive direction.  What friction force acts on the mass?

 

      A) 2.0 N

      B) 3.0 N

      C) 4.0 N

      D) 5.0 N

 

 

 

 

 

23. A 10-kg mass slides down a flat hill that makes an angle of 10° with the horizontal.  If friction is

      negligible, what is the resultant force on the sled?

 

      A) 1.7 N

      B) 17 N

      C) 97 N

      D) 98 N

 

24. A mass is placed on a smooth inclined plane with an angle of 37° to the horizontal.  If the inclined

      plane is 5.0-m long, how long does it take for the mass to reach the bottom of the inclined plane

      after it is released from rest?

 

      A) 1.3 s

      B) 1.2 s

      C) 1.1 s

      D) 1.0 s

 

25. An object with a mass m slides down a rough 37° inclined plane where the coefficient of kinetic

      friction is 0.20.  What is the acceleration of the object?

 

      A) 4.3 m/s2 

      B) 5.9 m/s2 

      C) 6.6 m/s2 

      D) 7.8 m/s2 

 

26. An object with a mass m slides down a rough 37° inclined plane where the coefficient of kinetic

      friction is 0.20.  If the plane is 10 m long and the mass starts from rest, what will be its speed at

      the bottom of the plane?

 

      A) 12 m/s

      B) 11 m/s

      C) 9.7 m/s

      D) 9.3 m/s

 

27. A bulldozer drags a log weighing 500 N along a rough surface.  The cable attached to the log

      makes an angle of 30.0° with the ground.  The coefficient of static friction between the log and the

      ground is 0.500.  What minimum tension is required in the cable in order for the log to begin to

      move?

 

      A) 224 N

      B) 268 N

      C) 289 N

      D) 500 N