Which of the following is not an example of a machine used as a force multiplier?

1. A jack used to lift a car.
2. A single fixed pulley used to lift a bucket of water from a well.
3. A bar used to lift a heavy stone.
4. A wheel barrow used to carry a load.

Which of the following statements is incorrect?

1. For a machine, velocity ratio does not change.
2. Due to friction, mechanical advantage of a machine increases.
3. For an ideal machine, work output is equal to the work input.
4. For an ideal machine, mechanical advantage is numerically equal to the velocity ratio

Unit of velocity ratio is:

1. Nm
2. Joule
3. Newton 
4. No unit

The correct relationship between the mechanical advantage (M.A.), velocity ratio (V.R.) and efficiency (η) is:

1. M.A. = η x V.R.
2. V.R. = η x M.A.
3. η = M.A. x V.R.
4. None of these