1. Bell Work
Ignoring the motion of the driver, observe the motion of the car before, and after the crash.
1. Identify as many changes in its motion as you can (This includes both speeds and directions).
2. Make a list of all the changes, and try to identify the forces that caused them.
Chapter 4.1

2. What is a Force?
An action exerted on an object which may change the object’s state of rest or motion.
Partner Experiment:
1. What does the force of the pusher’s hand translate to the pushed?
2. What is force proportional to?
3. Is force a vector or a scalar?

3. Types of Forces 2 Basic Types: 4 Fundamental Forces Contact & Field
Strong
Weak
Electromagnetic
Gravitational

4. Units of Mass, Acceleration, and Force
SI Units (page 121)
Units of Mass, Acceleration, and Force
System
Mass
Acceleration
Force SI
cgs g
cm/s2
dyne=g*cm/s2
Avoirdupois
slug
ft/s2
lb=slug*ft/s2

5. 1 lb. = 4.448 N 1 N = 0.225 lb. Conversions Quick Experiment:
1. Weigh yourself on the scale provided.
2. Convert your wright from Newton's to lbs.

6. The unit for pound, is written as lb. Why?

7. Libra
Latin word for pound
lb.

8. Free Body Diagrams

9. A skydiver is descending with a constant velocity.
Consider air resistance.

10. Rightward force is applied to a book in order to move it across a desk at constant velocity.

11. A college student rests a backpack upon his shoulder.
A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity.
An egg is free-falling from a nest in a tree. Neglect air resistance.
A girl is suspended motionless from the ceiling by two ropes.
A car is coasting to the right and slowing down.