Force and Acceleration

Force and acceleration for year 10 science

1. FORCE
To cause an object to change velocity (ie to accelerate) we
need to apply a force.
Force Acceleration
Force
Acceleration
Small force = small acceleration
Double the force = double the acceleration

2. Force
Acceleration
Small force = small acceleration
Same force, half the weight = double the acceleration
Acceleration
Force
Force Acceleration
Same force, double the weight = half the acceleration

3. Newton’s Second Law
The idea that acceleration depends upon how big
the force is, and how heavy the object, is called
Newtons Second Law of Motion
It can be stated in the equation:
Force = mass x acceleration
F = ma
Force is measured in newtons (N)
Mass is measured in kilograms (kg)
Acceleration is measured in m/s
2

4. Newton’s Second Law
F = ma
can be rearranged:
a =
F
m =
F
m a

5. What force is required to
accelerate a 1500 kg car
at 3 m/s
2
?
m = 1500 kg a = 3 m/s
2


F = ma
= 1500 x 3
= 4500 N
What force is applied to a
300 g cricket ball that
accelerates at 20 m/s
2
?
m = 0.3 kg a = 20 m/s
2

F = ma
= 0.3 x 20
= 6 N
FORCE: EXAMPLES (1)

6. A force of 8 N is applied
to a mass of 2 kg. What
is the acceleration?
F = 8N m = 2 kg

a = F
m
= 8
2

= 4 m/s
2

A force of 200 N causes an
object to accelerate at 5
m/s
2
. What is its mass?
F = 200 N a = 5 m/s
2
m = F
a
= 200
5

= 40 kg
FORCE: EXAMPLES (2)