Question

A car of mass 2000 kg is lifted up a distance of 30 m by a crane in 1minute. A second crane dies the same job in two minutes (g=9.8ms-2) so now, the power supplied by 1st crane is? The works done by the two cranes are?

Answer 1

work done=force*displacement
force=mass*accel.
=2000*9.8=19600N
therefore the work done by first crane =19600*30J=588000J
power=work/time=588000/60=9800J
therefore power of first crane is 9800J


work done by second crane is 58800/120=490J

Answer 2

w=mgh

w=2000x9.8x30=60000x9.8=588000J

power=work^time

= 588000by120 sec

= 490J