Question

28 which of the following is a situation where an objects speed is constant but its velocity is changing? a a car turns a corner at 20 m/s b a car drives in a straight line at 20 m/s c a car turns a corner while speeding up from 0 m/s to 20 m/s d a car speeds up from 0 mph to 20 m/s

Explanation:

Speed is a scalar quantity (only magnitude), while velocity is a vector quantity (magnitude and direction).

• Option A: The car's speed is \(20\ m/s\) (constant magnitude), but when it turns a corner, its direction changes. Since velocity depends on direction, the velocity changes.
• Option B: The car moves in a straight - line at \(20\ m/s\). Both speed (magnitude \(20\ m/s\)) and direction (straight - line) are constant. So, velocity is constant.
• Option C: The car is speeding up (magnitude of speed changes from \(0\ m/s\) to \(20\ m/s\)), so speed is not constant. Also, direction changes as it turns the corner.
• Option D: The car is speeding up (magnitude of speed changes from \(0\ m/s\) to \(20\ m/s\)), so speed is not constant.

Answer:

A. a car turns a corner at 20 m/s