1. Forces in Motion

2. Galileo proved that the rate at which an object falls is not affected by the mass.

3. If three balls of different materials were dropped at the same time from the same height, which would hit the ground first? (Assume there is no air resistance.) They would hit at the same time.

4. Air resistance is fluid friction.

5. The amount of air resistance acting on an object depends on the object’s size and shape.

6. ____ is reached when a falling object stops accelerating. The object is falling at a constant speed. Terminal velocity

7. Parachutes slow skydivers to a safer terminal velocity because parachutes increase air resistance.

8. An object is in ____ only if gravity is pulling it down and no other forces are acting on it. free fall

9. ____ is a measure of gravitational force. Weight

10. Astronauts float inside the space shuttle because they are in free fall.

11. Orbital motion is a combination of forward motion and free fall.

12. The unbalanced force that causes objects to move in a circular path is called centripetal force.

13. ____ is the curved path an object follows when thrown or propelled near the surface of Earth. Projectile motion

14. The curved path traveled by a thrown baseball is known as projectile motion.

15. Because of projectile motion, when aiming at a target you should always aim above the bull’s eye.

16. Catapults create projectile motion.

17. According to Newton’s first law of motion, a moving object that is not acted on by an unbalanced force will remain in motion.

18. ____ is the tendency of all objects to resist any change in motion. Inertia

19. ____ is the amount of matter in an object, and its value does not change. Mass

20. If a car driver suddenly makes a sharp turn, the passenger slides to the side of the car because of inertia.

21. According to Newton’s second law of motion to increase acceleration you must increase force or decrease mass.

22. Newton’s third law of motion states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.

23. ____ is a property of a moving object that depends on the object’s mass and velocity. Momentum

24. A golf ball and a bowling ball are moving at the same velocity. Which has more momentum? The bowling ball, because it has more mass.

25. When you bump into someone standing still, you can knock them over because of momentum.