Question

stamp: what is acceleration in physics?
acceleration is the change in velocity (increase or decrease) over a period of time.
the formula for acceleration is a=(v_f - v_i)/t
a: acceleration
v_f: final velocity
v_i: initial velocity
t: time

truck moving with constant velocity
bicycle speeding up
car slowing down
book at rest on a table

Explanation:

Acceleration occurs when there is a change in velocity. A truck moving with constant velocity has no change in velocity, so no acceleration. A book at rest on a table has zero velocity and no change in velocity, so no acceleration. A bicycle speeding up has an increase in velocity, so it has acceleration. A car slowing down has a decrease in velocity, so it also has acceleration.

Answer:

bicycle speeding up, car slowing down