Worked Examples on Power

• Calculate the power generated by a man of weight 500N if he runs up a road, 5m high in 2seconds.

SOLUTION

Weight = 500N, d= 5m, t = 2s

Power = ?, work done =?, t = 2

Work done = force x distance

      = 500N x 5m

      = 2500 J

Power = work done / time

      = 2500 J / 2s
      = 1250 W

• A force of 20N was used to lift a load through a distance of 5m in 10s. Calculate power.

SOLUTION

Force = 20N, distance = 5m, time = 10s

Power = work done / time

Work done = force x distance

      = 20N X 5m
      = 100J

Power = 100J / 10s

      = 10W

• A man weighs 50kg, he runs a distant of 5m in 2s.what is the power of the man? [Take acceleration due to gravity to be 10ms-²]

SOLUTION

Energy used = mass x acceleration due to gravity x height

        = 50 x 10 x 5
        = 2500J

Power = energy used / time taken

        = 2500 / 2
        = 1250W