Question

A car initially moves along a straight road at 50 km/hr, and then turns around to travel at 80 km/hr in the opposite direction. What is the car's change of velocity?

Answer 1

Answer on Question #72530-Physics-Other

A car initially moves along a straight road at 50 km/hr, and then turns around to travel at 80 km/hr in the opposite direction. What is the car's change of velocity?

Solution

The initial velocity is

$$v_{i} = -50 \frac{\mathrm{km}}{\mathrm{hr}}.$$

We can choose positive and negative direction as we need. I cannot see why initial velocity should be positive according to given scenario.

The final velocity is

$$v_{f} = 80 \frac{\mathrm{km}}{\mathrm{hr}}.$$

The car's change of velocity is

$$\Delta v = v_{f} - v_{i} = 80 \frac{\mathrm{km}}{\mathrm{hr}} - \left(-50 \frac{\mathrm{km}}{\mathrm{hr}}\right) = 130 \frac{\mathrm{km}}{\mathrm{hr}}$$

Answer: $130 \frac{\mathrm{km}}{\mathrm{hr}}$