An electric motor is rated at 250 W. In a physics experiment, it is used to lift a load performing 7500 J of work. What does the rating indicate in this context?
The motor can perform 7500 J of work in 30 seconds at full power
Power rating tells how fast a machine can do work, i.e. the work done per second: \(P = \frac{W}{t}\).
A rating of 250 W means the motor can do 250 J of work every second at full power.
Time needed for 7500 J of work: \(t = \frac{W}{P} = \frac{7500}{250} = 30\) s.
The rating does not cap the total work ever done (that depends on how long it runs), it is not stored energy (power is a rate, not an amount of energy), and watt is not a unit of force (force is measured in newtons).
Hence, the answer is The motor can perform 7500 J of work in 30 seconds at full power.
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