7 If a man lifts a load up with the help of a rope such that it raises the - Science - Work and Energy

Question

7 If a man lifts a load up with the help of a rope such that it
raises the load of mass 50kg
to a height of 20m in 100 sec Find the power of man
8 A ball is dropped from a height of 5m Find the velocity of the
ball just before it
reaches the ground Do you require the value of mass to find the
velocity?
9 Two persons A and B do same amount of work The person A does
that work in t1sec
and the person b in t2sec Find the ratio of power delivered by
them

Hansraj Rai · Accepted Answer

7 power = work done / time work done = mgh = 50Ã—9 8Ã—20 = 9800 J time , t = 100 sec power = 9800/100 = 98 Watt 8 s = 5 m , u =0 m/s , v = ? a = 9 8 m/s2 Using the eq , $v^{2} - u^{2} = 2 a s v^{2} - 0 = 2 \times 9 8 \times 5 v = 9 9 m / s$ 9 Use the formula , power = work/time work done = W $P_{A} = \frac{W}{1} P_{B} = \frac{W}{2} \frac{P_{A}}{P_{B}} = 2$