Your body is now resisting to the change from standing still to moving forwards and this time you fall backwards. You must have observed your driver, mechanic or even your father changing his punctured car tyre. Lifting a car is as such impossible. But it needs to be done to change a wheel. To accomplish this task, the driver uses a jack.
Most jacks have a screw that can turn inside a nut.
A screw is a simple machine. It has a ridge, called a thread, cut around it in form of a spiral. It is a special kind of an inclined plane. To turn a screw you apply a turning force to the head of the screw. When you turn the head of the screw round once, the screw moves forward.