Newton's First Law (WJEC GCSE Science (Double Award)): Revision Note
Newton's First Law of Motion
Higher Tier Only
Newton's first law of motion states:
Objects will remain at rest, or move with a constant velocity unless acted on by a resultant force
This means if the resultant force acting on an object is zero:
The object will remain stationary if it was stationary before
The object will continue to move at the same velocity if it was moving
When the resultant force is not zero
The speed of the object can change
The direction of the object can change
Objects with Zero Resultant Force
Constant velocity can only be achieved when the forces on an object are balanced - in other words, when the resultant force is zero
Worked Example
If there are no external forces acting on the car and it is moving at a constant velocity, what is the value of the frictional force, F?
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
This means the driving and frictional forces are balanced
Step 3: State the value of the frictional force
Frictional force, F = driving force = 3 kN
Examiner Tips and Tricks
Higher-tier students must be able to state Newton's first law from memory. Other students just need to be able to understand it and identify examples of it in action.
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