Newton's First Law (Oxford AQA IGCSE Physics)
Revision Note
Written by: Leander Oates
Reviewed by: Caroline Carroll
Newton's First Law
What is Newton's first law of motion?
If the resultant force acting on an object is zero:
A moving object will continue to move at the same velocity
A stationary object will remain at rest
This is Newton's first law of motion
You may also see it written as:
Objects will remain at rest, or move with a constant velocity unless acted on by a resultant force
Objects with zero resultant force
There is zero resultant force acting on objects when the forces acting on the objects are balanced
Worked Example
A car travels in a straight line at a constant velocity.
Determine the magnitude of the frictional force acting on the car.
Answer:
Step 1: Recall Newton's first law of motion
Newton's first law of motion states that objects will remain at rest, or move with a constant velocity unless acted on by a resultant force
Step 2: Relate Newton's first law to the scenario
Since the car is moving at a constant velocity, there is no resultant force acting
This means the driving and frictional forces are balanced
Step 3: State the value of the frictional force
Frictional force = driving force
Frictional force = 3 kN
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