Chapter 4

Question 1

What are the two types of forces?

Answer 1

Contact- physical contact
Field- object creates an invisible field around it that can exert a force on objects that interact with it
Ex on slide 18

Question 2

What is Newton’s first law?

Answer 2

An object that moves with a constant velocity or stays at rest has zero net force working on it

Question 3

What is inertia?

Answer 3

Tendency of an object to continue its motion in the absence of force
Also means the tendency of an object to resist changes in its motion

Question 4

What is Newton’s second law?

Answer 4

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass
ΣF=ma
a=ΣF/m
ΣFx=max, ΣFy=may

Question 5

What is Newton’s law of gravitational force?

Answer 5

Describes gravitational forces of attraction that any two object exert on one another
F=Gm1m2/r^2
r is distance between centres
G is constant
Derivation besides slide 20 sept 28

Question 6

What is weight?

Answer 6

Gravitational force on an object
W
W=mg
G is acceleration do to earths gravity

Question 7

What is Newton’s third law?

Answer 7

Forces always occur in pairs

For every action there is an equal but opposite reaction

Question 8

What is the normal force?

Answer 8

Perpendicular contact force to surface
n
Examples on slide 19
Cases on how to solve for n on page 92-94

Question 9

What is the two forces of friction?

Answer 9

Static- at rest
Kinetic- frictional forces in motion
fs< μs•n ; fs (max) = μs•n
fk= μk•n
Example on slide 18 oct 3

Question 10

What are tension forces?

Answer 10

Exerted through rope string, etc
Used to pull not push so force is away from object
Example on slide 26
Cases in how to deal with it on page 98-99

Question 11

What are two body problems?

Answer 11

Problems with two masses connected

ΣFext=(ΣMint)Asys