Simple Machines Physics - Simple Machines

There is no gain in mechanical advantage in the case of a single fixed pulley. Explain, why the pulley is then used?

Name a machine which can be used to multiply force and change the direction of force applied.

Write an expression to show the relationship between mechanical advantage, velocity ratio, and efficiency for a simple machine.

What is the efficiency of an ideal machine?

Give an example where a machine is used to obtain gain in speed.

Comment on the statement ‘The mechanical advantage of a machine is greater than 1’. Give an example of a lever mechanical advantage is:
(i) greater than 1.
(ii) Equal to 1.

Define mechanical advantage (M.A.) of the machine.

Give two reasons why the efficiency of a single movable pulley system is not 100%?

What is a single fixed pulley? State its one use.

Which type of lever has a mechanical advantage always more than one? Give one example. What change can be made in this lever to increase its mechanical advantage?

In a single movable pulley system, a load of 125 kgf is lifted by an effort of 75 kgf. Find the percentage efficiency of system.

A crowbar of length 100 cm is used to lift a load of 5 kgf. It has its fulcrum at a distance of 20 cm from the load. Calculate:
(i) the mechanical advantage of a crowbar and,
(ii) the effort applied at the other end.

The length of a nut-cracker is 12 cm. A nut, when kept at a distance of 4 cm from its fulcrum, requires an effort of 100 gf to crack it. What force will be required to crack the nut without using the nut-cracker?

Define Velocity Ratio

A man raises a load of 360 kgf using a block and tackle system of 3 pulleys. If the efficiency of the pulley system is 60%, what effort is applied by the man?

A ‘block and tackle’ system used 3 pulleys in the lower block and 4 pulleys in the upper block. What is the ‘velocity ratio’ of this system? If the load is to be lifted by a person capable of applying a maximum effort of 1000 N, what is the maximum load than can be lifted under ideal conditions?
The actual maximum load that gets lifted turns out to be 6300 N. What are the values of the actual M.A. and efficiency of the set-up?

If the weight of the movable pulley is W, obtain the expression for MA, VR, and efficiency.

A cook used a ‘fire tong pair’ of length 32 cm. to lift a piece of burning coal of mass 500 g. If he applies his effort at a distance of 8 cm from the fulcrum, what is his effort? Assume friction etc. to be absent. Also, obtain values of the M.A. and the V.R. of this ‘machine’.