Question

You apply a horizontal force of 10.0 N to pull a wheeled suitcase at a constant speed of 0.5 m/s across flat ground. How much power is used?

Answer 1

$P=\frac{dW}{dt}=\frac{d}{dt}(Fr)=F\frac{dr}{dt}=Fv$

$P=Fv$
$P=(10.0N)(0.5\frac{m}{s})$
$P=\frac{5N-m}{s}$
$P=\frac{5J}{s}$
$P=5W$