Question

1. garage door opener is rated at 373 W. In 14.0 s of operation the opener can do ___x10³ J of work. (Give your answer with the correct number of sig digs and do not include units)

2.An automobile engine exerts a force of 595 N to propel the car at 90.0 km/h on a level road. The power output of the engine at that time is ___x10⁴ W. (Give your answer with the correct number of sig digs and do not include units)

Answer 1

1)

$$P=\dfrac{W}{t},$$ $$W=Pt=373\ W\cdot14\ s=5.2\cdot10^3\ J.$$

2)

$$P=Fv=595\ N\cdot25\ \dfrac{m}{s}=1.5\cdot10^4\ W.$$