## Glossary of Bob Jones Science 9 Chapter 13 Mechanics

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- The modern study of motion...
- mechanics 13A

- What is the proper way to begin the study of motion?
- by describing motion 13A

- The two parts of motion...
- kinematics (the description of how things move) dynamics (why things move) 13A

- A group of landmarks used to study motion.
- frame of reference

- Change in position of an object...
- displacement 13A

- Displacement over time...
- speed 13A

- Formula for velocity (or speed in a certain direction)
- v=d/t 13A

d=distance

t=time

units will be in m/s or km/hr

- Formula for acceleration...
- a=vf-vi

_____

t

vf=final velocity 13A

vi=initial velocity

- Newton's first law of motion...
- an object in motion will stay in motion and an object at rest will stay at rest unless it is acted on by a force 13B

- The resistance to change in motion...
- inertia 13B

- Newton's second law of motion...
- The value of an unbalanced force is equal to its mass times its acceleration

F=ma 13B

- Unit of force...
- newton (N)

which are kg m/s2 13B

- Newton's third law of motion...
- For every action, there is an opposite and equal reaction 13B

- Rockets take off by...
- action-reaction forces

(third law)

- What motion law are these:

When you car stops, you are thrown forward and a rocket in space doesn't have to burn feul to keep going straight? - First law

- What motion law are these: when air resistance balances gravity, raindrops stop accelerating and a light bike can accelerate faster?
- Second law

13B

- What law are these: When you lean against a wall, it supports you and when you dive from a boat, it moves backward.
- third law

13B

- Quantities that give only magnitude such as speed, distance, or force are...
- scalar 13A

- Quantities that give magnitude and direction such as velocity are...
- vectors 13A

- A triangle symbol means...
- change in 13A

- Forces (such as gravity) that act on objects without touching them...
- action-at-a-distance forces 13C

- Who was the scientist that first experimented with gravitational attraction...
- Galileo 13C

- If a book and a bowling ball are dropped out of a plane which would hit first?
- Both would hit at same time. 13C

- If you drop a book and a feather on Earth and on the Moon, what would be different?
- The book would hit first on Earth because the feather would have air resistance, but on the moon, they would hit together. 13C

- On Earth, the acceleration due to gravity is..
- 9.8 m/s2

- The distance that an accelerating object travels...
- d=1/2 a t2

- The highest velocity at which an object can fall...
- its terminal velocity (when gravity is exactly balanced by resistance of the fluid its falling in)

- Universal law of gravitation...
- m1 time m2

F=G x __________

d squared

- G in the universal gravitation formula is a fundamental...
- physical constant

- Satellites are...
- celestial bodies in orbit around another celestial body