Newton's First Law (AQA GCSE Physics): Revision Note

Lima did some online research and found out that the Moon orbits the Earth at a constant speed of around 2000 mph. She says that this is not an example of Newton's first law of motion. Is Lima correct? Explain your answer.

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: Determine if the object in the question is at rest, or if it is moving with a constant velocity

• The Moon, in this case, is not at rest

• It is moving at a constant speed

• But it is not moving in a constant direction - it continually orbits the Earth

• Hence, it is not moving with a constant velocity, because velocity is a vector quantity

Step 3: State and explain whether Lima is correct

• Lima is correct

• The Moon moves with a constant speed, but always changes direction

• So it is not moving with a constant velocity, and is not an example of Newton's first law of motion