8. What is the magnitude of the horizontal component of a 27.0 N force on a wagon being pulled at an angle of 42.0° above horizontal?
9. A ball is thrown with a velocity of 3.0 m/s at an angle of 30° below horizontal. Its vertical velocity is zero when:
a. The ball is at its maximum height
b. Just before the ball hits the ground
c. When the ball changes direction
d. Never during the ball's flight
10. Which of the following are true?
a. Centripetal force always acts away from the center of rotation.
b. Centripetal force is not an independent force but some other force acting centripetally due to the geometry of the problem.
c. Centripetal acceleration is inversely proportional to the magnitude of speed squared.
d. All options are true.
11. Which of the following is a non-inertial frame of reference?
a. A person travelling at a constant velocity in a car observes a person jogging along the sidewalk.
b. A child on a merry-go round observes his sibling standing on the ground and waving.
c. A person in a stationary train throws a ball.
d. A person on the platform watches a ball thrown by the person on the stationary train.
12. If a train with two cars is being pulled up a hill, the force between the two cars is:
a. An action reaction force pair
b. Called the tension
c. Equal in magnitude and opposite in direction
d. All of the options are true
13. In a pulley problem:
a. The tension changes if there is friction present
b. The tensions must have opposite signs
c. The heavier block determines the magnitude of the acceleration
d. None of the options are true
14. A piano is being pushed by two movers. One mover applies a force of 200 N [N], the other applies a force of 210 N [N20°E]. Which method could be used to determine the net force?
a. Newton's 2nd law
b. Collinear vector addition
c. Vector addition using a Pythagorean triangle
d. Vector addition by components
15. What happens to the force required for an object to maintain circular motion as the radius doubles?
a. Force doubles
b. Force quadruples
c. Force is halved
d. Force doesn't change