Question

Can you conclude that a car is not accelerating if its speedometer indicates a steady$60\mathrm{km}/\mathrm{h}$? Explain.

Short answer

No, based on the speedometer reading, you cannot conclude that a car is not accelerating.

Step-by-step solution

Step 1. Definitions of velocity and acceleration

Velocity and acceleration are vector quantities. Velocity is defined as the rate of change of displacement of an object with time, and acceleration is defined as the time rate of change of velocity.

The SI units of velocity and acceleration are $\mathrm{m}/\mathrm{s}$and $\mathrm{m}/{\mathrm{s}}^2$, respectively.

Step 2. Analysis of the car’s acceleration

A speedometer measures only the speed of a car. In the given case, it indicates that the car is moving at a constant speed of $60\mathrm{km}/\mathrm{h}$. However, it does not mean that the car also has a constant velocity.

If the car travels along a curve or a winding road, its direction will change even at the same speed ($60\mathrm{km}/\mathrm{h}$). And it will also have some acceleration.