9. Newton's Laws of Motion

Question 1

State Newton’s 1st law of motion

Answer 1

The velocity of an object will not change unless a resultant force acts on it

Question 2

What does Newton’s 1st law of motion mean?

Answer 2

A body will stay still or move in a straight line at a constant speed unless there’s a resultant force acting on it

Question 3

State Newton’s 2nd law of motion

Answer 3

The acceleration of an object is proportional to the resultant force acting on it

Question 4

What equation is related to Newton’s 2nd law of motion?

Answer 4

F = ma

F = Resultant force (N)
m = Mass (kg)
a = acceleration (m/s^2)

Question 5

What does F = ma show?

Answer 5

1. The more force acting on a certain mass, the more acceleration you get
2. The more mass you have, the less acceleration you get for a certain force

Question 6

What direction is the acceleration measured in?

Answer 6

The same direction as the resultant force

Question 7

State Newton’s 3rd law of motion?

Answer 7

If an object A exerts a force on object B, then object B exerts an equal but opposite force on object A

Question 8

Name 3 examples of Newton’s 3rd law of motion

Answer 8

1. If you push against a wall, the wall will push back against you, just as hard. Once you stop pushing, so does the wall
2. If you pull a cart, whatever force you exert on the rope, the rope exerts the exact opposite pull on you
3. When you go swimming, you push back against the water with your arms and legs, and the water pushes you forwards with an equal-sized force

Question 9

When does Newton’s 3rd law of motion apply?

Answer 9

When the pairs of forces are of the same type (e.g. both gravitational or both electrical)