8. A bob is suspended with the help of a thread whose breaking load is twice the weight of
the bob. Taking g=10m/s?, what is the
minimum time in which the bob can be raised
by 10m?

An ideal otto cycle has a compression ratio of 10.5, takes in air at 90 kpa and 40°c, and is repeated 2500 times per minute. using constant specific heats at room temperature, determine the thermal efficiency of this cycle and the rate of heat input if the cycle is to produce 90 kw of power.