6.5.4.2 Forces, acceleration and Newton's Laws of Motion

Question 1

What is Newton’s First Law of Motion?

Answer 1

An object will only accelerate if a resultant force is acting.

Question 2

What three things can an object do while accelerating?

Answer 2

Speed up
Slow down
Change direction

Question 3

If the resultant force is zero, what two motions are possible?

Answer 3

The object is stationary

The object moves at a constant velocity (speed and direction)

Question 4

What two (horizontal) forces act on a car travelling at constant speed along a flat road? What can you say about the size of these forces?

Answer 4

Driving force or thrust forwards
Friction and air resistance backwards
They are the same

Question 5

A plane flies along at a constant velocity and height. What can you say about the size of the air resistance and thrust?

Answer 5

They are the same

Question 6

A plane flies along at a constant velocity and height. What can you say about the size of the weight and the lift?

Answer 6

They are the same

Question 7

What is Newton’s Second Law in words?

Answer 7

The acceleration of an object is proportional to the forces and inversely proportional to the mass.

Question 8

What is Newton’s Second Law as an equation?

Answer 8

Force = mass x acceleration

Question 9

What is the unit of force?

Answer 9

Newtons (N)

Question 10

What is the unit of mass?

Answer 10

kilograms (kg)

Question 11

What is the unit of acceleration?

Answer 11

metres per second squared (m/s2)

Question 12

What is the typical acceleration of a lorry?

Answer 12

~ 0.5 m/s2

Question 13

What is the typical acceleration of a car

Answer 13

~ 2.0 m/s2

Question 14

What is Newton’s Third Law?

Answer 14

Whenever two objects interact, the forces on them are equal and opposite (of the same type and act on the other object)

Question 15

In a Newton’s Third Law pair the forces can be different. True or False

Answer 15

False

Question 16

In a Newton’s Third Law pair the forces can act on the same object. True or False

Answer 16

False

Question 17

In a Newton’s Third Law pair the forces are the same size. True or False

Answer 17

True

Question 18

What is the Newton’s Third Law pair for the weight of a book sitting on a table?

Answer 18

The weight of the Earth being pulled up towards the book.

Question 19

What is the Newton’s Third Law pair for the (normal) reaction force of a book sitting on a table?

Answer 19

The normal reaction force of the book acting on the table.

Question 20

In a Newton’s Third Law pair the forces at in opposite directions. True or False

Answer 20

True