1. Lots of fun! Win valuable prizes!

2. Wednesday’s test Newton’s three laws of motion Calculations with net force (ΣF = ma) Free-body diagrams Mass vs. weight Centripetal acceleration Centripetal force Universal gravitation Torque Rotational equilibrium (balanced torques) Textbook Ch. 4 (omit coefficient of friction), Ch. 7 sections 1,2,4 (omit simple machines)

3. 1. As a ball falls, the action force is the pull of the Earth on the ball. What is the reaction to this force? A. The pull of the ball on the Earth B. Air resistance acting against the ball C. The acceleration of the ball D. Nonexistent in this case E. none of the above

4. 2. A 75-kg astronaut weighs 662 N on the surface of Venus. What is g, the acceleration of gravity, on Venus?

5. 3. Draw a free-body diagram of a car accelerating to the left on a level road. Neglect friction.

6. 4. A 15-N force and a 32-N force act on an object toward the right. A 18-N force acts on the same object toward the left. The object weighs 2.5 N and is supported by a horizontal surface. What is the magnitude and direction of the net force on the object?

7. 5.Torque is defined as _____. A. mass times velocity B. force times lever arm C. momentum times radius D. force times time E. mass times acceleration

8. 6. A model rocket has a mass of 1.47 kg. At launch the rocket’s engine exerts an upward force of 40.2 N. What is the acceleration of the rocket?

9. 7. An object weighs 30 N on Earth. A second object weighs 30 N on the moon. Which has the greater mass? A. The one on Earth B. The one on the moon C. They have the same mass. D. Not enough information to say

10. 8. A 25-kg crate is pulled across the ice with a rope. A horizontal force of 62 N is applied to the rope. If the force of friction between the crate and the ice is 22 N, what is the acceleration of the crate?

11. 9. A force of 12 N is applied to a doorknob located 1.25 m from a door’s hinges. What is the magnitude of the torque about the hinges if the angle between the direction of the applied force and the door surface is 50°?

12. 10. What is the gravitational force acting on a 7.5 x 10 8 kg oil tanker due to a 4.4 x 10 9 kg iceberg floating 672 m away?

13. 11. A car travels in a circle with constant speed. The net force on the car A. is directed forward, in the direction of travel. B. is zero because the car is not accelerating C. is directed toward the center of the curve. D. none of the above

14. 12. An object weighs 20 N on the earth's surface. What is the weight of the object on a planet that has four times the earth's mass and twice the earth's radius?

15. 13. An airplane is flying in a horizontal circle of radius 1,500 m with a speed of 125 m/s. What is the magnitude of the centripetal acceleration of the plane?

16. 14. A 40-kg boy sits on a seesaw 2.0 m from the fulcrum. What distance from the fulcrum should a 30-kg girl sit in order to balance the seesaw?

17. Bonus question time!

18. Wile E. Coyote is chasing the Roadrunner while coasting on roller skates at 21 m/s. He lights a rocket on his back, which boosts his velocity to 98 m/s before it burns out 5.5 seconds later. What is the net force acting on Wile E. and his gear, which have a combined mass of 68 kg?