1. Laws of Motion Review

2. Vocabulary Acceleration Coefficient of Friction Equilibrium Force
Free Body Diagram
Inertia
Kinetic Friction
Mass
Motion
Net Force
Newton
Rolling Friction
Static Friction
Terminal Velocity
Vector

3. Categories of Forces Contact – direct contact or touch between objects
Long Range – acts at a distance

4. Types of Forces Pushing a crate across the floor – Applied
Air Friction - Drag
Opposes motion – Friction
Support force – Normal
Created in a rope, etc when connected to another mass – Tension
Force due to gravity – Weight
Are the forces above contact or long range?

5. Free Body Diagrams
Pictorial diagram of all the forces acting on an object
The length of the arrow is proportional to the magnitude of the force
How is the normal force drawn?
How is weight drawn?

6. Free Body Diagram Practice
Draw a FBD for the following:
A flowerpot falls freely from a windowsill.
A skydiver falls at a constant velocity.
A cable pulls a box across a table. The box accelerates even though friction is present.
A rope lifts a bucket.

7. Net Force The vector sum of all forces acting on an object
Calculated for both the x and the y
Represented by ΣF

8. Net Force Practice
Pictorial diagram of all the forces acting on an object
The length of the arrow is proportional to the magnitude of the force

9. 1st Law of Motion Law of Inertia
An object at rest will stay at rest, an object in motion will stay in motion unless acted upon by an unbalanced force greater than zero
Ex. A car rider continues forward when the driver suddenly applies the brakes

10. 2nd Law of Motion ∑F = ma W = mg Ff = µFn What is the net force?
What is the unit for mass?
Is mass the same quantity as weight?
What is g?
What is μ?
On a flat surface, what is equal to the Fn ?

11. 2nd Law Practice
If all of the forces acting on an object balance so that the net force is zero, then
A. The object must be at rest
B. The object must be at a constant velocity
C. The object may be at rest or at a constant
velocity

12. 2nd Law Practice
Two astronauts tug on opposite sides of a satellite. The first astronaut tugs to the left with a force of 30 N. With what force does the second astronaut tug in order to keep the satellite moving toward him at a constant velocity of 20 m/s?
A. 30 N
B. – 30 N
C. 0 N
D. 50 N
E. 1.5 N

13. 2nd Law Practice
The maximum (or terminal) velocity of a skydiver (m=70kg) with arms and legs extended is about 120 mi/h (= 53.6 m/s). What force does air resistance exert on the skydiver?
A. 0 N
B. 13 N
C. 70 N
D. 700 N
E N

14. 2nd Law Practice
An airplane has a mass of 3.1 x 104 kg and takes off under the influence of a constant net force of 3.7 x 104 N. What is the acceleration that acts on the plane?

15. 2nd Law Practice Weight and mass are A. always the same
B. inversely proportional
C. based on location
D. none of the above

16. 2nd Law Practice
A large (150 kg) refrigerator needs to be moved across the kitchen. Fred pulls with a force of 100 N and Wilma pulls with 75 N in the same direction. If the force of friction was 40 N, what will be the acceleration of the refrigerator?
A 1.17 m/s2
B 0.90 m/s2
C 0.43 m/s2
D 135 m/s2

17. 2nd Law Practice
When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal velocity. This means that
a. the acceleration is equal to g.
b. the force of air resistance is equal to zero.
c. the effect of gravity has died down.
d. the effect of gravity increases as he becomes closer to the ground.
e. the force of air resistance is equal to the weight of the parachutist.

18. 2nd Law Practice
The force of kinetic friction is always __________ than the force of static friction.
a. less than
b. equal to
c. greater than
d. varies depending on situation

19. 2nd Law Practice
The normal force acts ______________ to the surface of the contact object
a. perpendicular
b. parallel
c. at an angle

20. 3rd Law of Motion
For every action, there is an equal and opposite reaction

21. 3rd Law Practice
A mass is suspended on a spring. The reaction force to the force of the gravity from the Earth acting on the mass is the force exerted by the
A. mass on the Earth
B. mass on the spring
C. spring on the mass
D. spring on the Earth
E. Earth on the mass