Answer: when you increase or decrease your speed.
Explanation:
Moving a skate at rest, you need to apply force in order to cause acceleration.
F = ma Where
F = force applied
m = mass of the skate
a = acceleration
The initial velocity u will be equal to zero and the skate will acceleration to a certain velocity.
as you skate down your neighborhood sidewalk, you will accelerate when you increase your speed. Because
Acceleration is the rate of change of velocity. That is,
Acceleration = change in velocity/ time.
And also, you will decelerate when you reduce the speed or velocity down your neighborhood sidewalk.
