Question

The speed of car, moving along a straight line (one-dimensional motion), will always slow down in which one of the following situations?
A. acceleration is negative
B. velocity is negative
C. velocity is negative and acceleration is positive

D. velocity and acceleration are both negative

Answer 1

Slowing down means velocity is decreasing.

Velocity is negative and acceleration is positive would be the correct option.

Reason: We may think that velocity is negative means the car is moving along negative X axis. Positive Acceleration means the car is accelerating along Positive X axis which means decelerating along negative X axis. Now, look along negative X axis where a car is moving and decelerating. Because of deceleration, the velocity will decrease.

Option A: Wrong because in which direction the car is moving is not mentioned.

Option B: Wrong because velocity can be constant. Hence, car won't slow down.

Option D: Wrong. Like previous argument, the car is moving and acceleration along negative X axis. Hence, velocity will increase along negative X axis.