Question

You need to purchase a motor to supply 400 joules [J] in 10 seconds [s]. All of the motors you can choose from are 80% efficient. What is the minimum wattage [W] on the motor you need to choose

Answer 1

32 W.

Step-by-step explanation:

Power: This can be defined as the ratio of energy to time. The S.I unit of power is watt(W). The formula for power is given as,

P = W/t.................... Equation 1

Where P = power, W = work done, t = time.

Given: W = 400 J, t = 10 s.

Substitute into equation 1

P = 400/10

P = 40 W.

If the motors that is choose is 80% efficient,

P' = P(0.8)

Where P' = minimum power

P' = 40(0.8)

P' = 32 W.