Question

Select three different examples of accelerated motion.

1 a body traveling in a straight line and increasing in speed
2 a body traveling in a straight line and decreasing in speed
3 a body traveling in a straight line at constant speed
4 a body standing still
5 a body traveling at a constant speed and changing direction

Answer 1

Remember the definition of acceleration:

a = Δv / Δt, this is change in velocity per unit of time.

Note that a and v are in bold to mean that they are vectors.

1) a body traveling in a straight line and increasing in speed: RIGHT:

Acceleration is the change in velocity, either magnitude or direction or both. So, a body increasing in speed is accelerated.

2) a body traveling in a straight line and decreasing in speed: RIGTH

A decrease in speed is a change in velocity, so it means acceleration.

3) a body traveling in a straight line at constant speed: WRONG.

That body is not changing either direction or speed so its motion is not accelerated but uniform.

4) a body standing still : WRONG.

That body is not changind either direction or speed.

5) a body traveling at a constant speed and changing direction: RIGHT.

The change in direction means that the body is accelerated. The acceleration due to change in direction is named centripetal acceleration.