I think it means doing work in physics
It does produce 'sound' ... a compression wave traveling through the air. But your ears don't hear a sound that's vibrating less than 20 or 30 times every second. If you could swing your pendulum that fast, you could hear the sound of its vibrations pushing the air around.
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.
