Question

current attempt in progress which one of the following situations does the object have no acceleration?
seeing a red traffic light ahead, the driver of a minivan steps on the brake. as a result, the minivan slows from 15 m/s to stop before reaching the light.
a ball is thrown upward from the surface of the earth, slows to a temporary stop at a height of 4 m, and begins to fall back toward the ground.
a boulder starts from rest and rolls down a steep mountain.
an elevator in a tall skyscraper moves upward at a constant speed of 3 m/s.
a ball at the end of a string is whirled in a horizontal circle at a constant speed.

Explanation:

Acceleration is a change in velocity (speed or direction).

• Minivan: Slowing down (speed change) → acceleration.
• Ball thrown up: Speed changes (slows, then falls) → acceleration.
• Boulder: Starts moving (speed change from rest) → acceleration.
• Elevator: Constant speed (no speed/direction change) → no acceleration.
• Ball in circle: Direction changes (even at constant speed) → acceleration.

Answer:

An elevator in a tall skyscraper moves upward at a constant speed of 3 m/s.