When do you have to get a job please help

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

During a car accident, a 125kg driver is moving at 31m/s and in 1.5s is brought to rest by an inflating air bag. what is the magnitude of the change in momentum to the driver

What is the specific heat of wood ?