Newton's First Law (Oxford AQA IGCSE Combined Science Double Award)
Revision Note
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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