Question

2 which of the following is a form of acceleration? select all that are forms of acceleration. a a truck is stopped at a red light, then gradually speeds up to the speed limit of 20 mi/hr (mph) b a car parked in a driveway c a plane flying due west at 550 miles per hour d a train travelling on straight track at 45 mi/hr, e a skydiver uses their parachute as they fall to slow down to 15 mi/hr (mph) f a race car drives around the curve in the track at 140 mi/hr.

Explanation:

To determine forms of acceleration, recall that acceleration is a change in velocity (speed or direction).

• Option A: The truck’s speed increases from 0 to 20 mph, so velocity changes (acceleration).
• Option B: The car is parked (speed = 0, no change) → no acceleration.
• Option C: The plane’s speed (550 mph) and direction (due west) are constant → no acceleration.
• Option D: The train’s speed (45 mph) and direction (straight) are constant → no acceleration.
• Option E: The skydiver’s speed decreases (slows down), so velocity changes (acceleration).
• Option F: The race car changes direction (around a curve) even at constant speed → velocity changes (acceleration).

Answer:

A. a truck is stopped at a red light, then gradually speeds up to the speed limit of 20 mi/hr (mph)
E. a skydiver uses their parachute as they fall to slow down to 15 mi/hr (mph)
F. a race car drives around the curve in the track at 140 mi/hr