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Which of the following is a typical use of a pulley in a building site?

To change the direction of force without changing its magnitude.

To reduce friction in moving parts.

To amplify the force required to move a load.

To lift heavy materials to a higher point.

What is a machine?

A device that helps in doing work by transmitting or transforming energy.

A device that does not require force to work.

A device that reduces the amount of force required to do work.

A device that changes the direction of the applied force.

Which of the following statements is true about the efficiency of a machine?

A machine can only be efficient if there is no friction.

The efficiency of a machine is always less than 100% due to energy losses like friction.

Efficiency is always greater than 100%.

Efficiency is the ratio of input energy to output energy.

In a pulley system, what is the mechanical advantage if the system has 3 pulleys?

Why is no machine 100% efficient?

Because machines always produce work at the same rate.

Because the machine always performs more work than the input.

Because some energy is always lost as heat due to friction.

Because it is impossible to transfer all energy in a machine.