A crowbar is used to pull a nail. The length of the effort arm of the crowbar is 28 cm and the resistance arm is 4.2 cm. What force in N is required to pull a nail if the friction force holding the nail in place is 120 N?

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.