Circular motion

Question 1

Why does an object travelling in a circular motion have a constant speed but varying velocity?

Answer 1

• Speed is a scalar quantity while velocity is a vector quantity
• When an object travels in a circle, its speed doesn’t change however, its direction is continuously changing
• As velocity is a vector quantity, it also takes direction into account. Therefore, if the direction is constantly changing then the velocity is also constantly changing

Question 2

Why is the moon in orbit accelerating?

Answer 2

• The moon’s velocity is constantly changing: velocity is a vector quantity. As its direction is changing, so is its velocity
• Acceleration is change in velocity over time. If the velocity is changing then so is the acceleration