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 speeds up from 0 mph to 20 m/s c a car drives in a straight line at 20 m/s d a car turns a corner while speeding up from 0 m/s to 20 m/s

Explanation:

• Speed is a scalar quantity (only magnitude). Velocity is a vector quantity (magnitude and direction).
• For option A: The speed is \(20\ m/s\) (constant magnitude). But when the car turns a corner, its direction of motion changes. Since velocity depends on direction, the velocity changes.
• For option B: The speed changes from \(0\) to \(20\ m/s\). So, both speed (magnitude) and velocity (as velocity magnitude changes) change.
• For option C: The car is moving in a straight - line at \(20\ m/s\). Both speed (magnitude \(20\ m/s\)) and velocity (constant magnitude and direction) are constant.
• For option D: The car is speeding up (speed magnitude changes from \(0\) to \(20\ m/s\)) and turning (direction changes). So, both speed and velocity change.

Answer:

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