Sometimes the acceleration is known and the net force is the question. What net force must act on a 900 kg car to accelerate it at 2.0 m/s²?
Rearrange a = F_net/m once, and the same solving steps carry every question like it.
Start from the equation you know: a = F_net/m.
Make F_net the subject: multiply both sides by m.
That gives F_net = m × a.
With m in kilograms and a in m/s², F_net comes out in newtons.
The answer is the net force: the combination of all the forces that must act on the car, not necessarily one applied force.
What net force is needed to accelerate a 900 kg car at 2.0 m/s²?
Write down the values in the question:
m = 900 kg
a = 2.0 m/s²
F_net = ?
Write down the equation:
a = F_net/m
Make F_net the subject:
F_net = m × a
Substitute in the values:
F_net = 900 × 2.0
Simplify:
F_net = 1800 N
The car needs an 1800 N net force.
A 65 kg sprinter leaves the blocks at 4.0 m/s². What net force acts on the sprinter?
Write down the values in the question:
m = 65 kg
a = 4.0 m/s²
F_net = ?
Write down the equation:
a = F_net/m
Make F_net the subject:
F_net = m × a
Substitute in the values:
F_net = 65 × 4.0
Simplify:
F_net = 260 N
The net force on the sprinter is 260 N.
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