Goyal Brothers Prakashan solutions for अ न्यू अप्रोच टू आईसीएसई [इंग्रजी] इयत्ता १० chapter 3 - Machines [Latest edition]

What is the principle of an ideal machine?

For a given machine (not ideal) prove:

\[\text{Efficiency}=\frac{\text{Actual mechanical advantage}}{\text {Ideal mechanical advantage}}\]

What is a machine?

State two functions of a machine.

With reference to machines define the following term:

Ideal mechanical advantage (I.M.A.)

With reference to machines define the following term:

Actual mechanical advantage (A.M.A.)

Define velocity ratio.

With reference to machines define the following term:

Ideal machine

Define the term efficiency of a machine.

Study the diagram alongside and answer the following questions:

1. What kind of lever is shown in diagram?
2. Derive ideal mechanical advantage of this lever.
3. Give two examples of this lever.

Study the diagram alongside and answer the following questions.

1. What kind of lever is shown in diagram?
2. Derive ideal mechanical advantage of this lever.
3. Give two examples of this lever.

Study the diagram alongside and answer the following questions.

1. What kind of lever is shown in diagram?
2. Derive ideal mechanical advantage of this lever.
3. Give two examples of this lever.

State the principle of a lever?

Explain why the mechanical advantage of the class III type of lever is always less than 1.

Name a class of lever which multiplies effort. Give one example.

Name a class of lever which multiplies speed. Give one example.

Why is it easier to open a lid with spoon, rather than with finger?

Describe three orders of levers giving an example of each. Draw neat diagrams showing the positions of fulcrum, load, and effort in each kind of lever.

A crowbar of length 120 cm has its fulcrum situated at a distance of 20 cm from the load. Calculate the mechanical advantage of the crowbar.

Diagram alongside shows a nut cracker.

1. What kind of lever is nutcracker?
2. Copy the diagram on it show the line of action of force for (i) effort, (ii) load.
3. What is the mechanical advantage of this lever?
4. Calculate the resistance offered by the nut, if an effort of 300 N is sufficient to crack it.

A spade of length 1 m is held by a person at a distance of 20 cm from the fulcrum. Calculate.

1. Velocity ratio of the spade.
2. Force required to lift a load of 40 N.

A machine can lift a useful load of 80 kgf and effort E. If the efficiency of machine is 80% and velocity ratio 5, calculate:

1. Actual mechanical advantage.
2. The value of effort E.

A cook uses a fire tong of length 28 cm to lift a piece of burning coal of mass 250 g. If he applies effort at a distance of 7 cm from the burning coal, what is the effort applied?

What is the relationship between the mechanical advantage and the velocity ratio for:

1. An ideal machine,
2. A practical machine.

Scissors and shears are levers of first order. However, the cutting edge of scissors used for cutting cloth is much longer than the cutting edges of shears used for cutting metals. Explain the difference.

Which class of lever has mechanical advantage always greater than one?

What change can be brought about in this lever to increase its mechanical advantage?

With reference to the terms mechanical advantage, velocity ratio and efficiency of a machine, name and define the term that will not change for the machine of a given design.

Match the movement of the body part in column A to the class of lever in column B.

The uniform plank of a seesaw is 8 m long and is supported at the centre. A boy weighing 50 kgf sits at a distance of 2.5 m from the fulcrum. Where must another boy weighing 40 kgf sit, so as to balance the plank?

In operating a water pump, a resistance of 480 N is overcome by an effort of 72 N. If the distance of the fulcrum from the point where the resistance acts is 0.2 m, find the distance from the fulcrum, where the effort is applied.

A uniform plank of a seesaw is 5 m long and supported at its centre. A boy weighing 40 kgf sits at a distance 1.5 m from one end of the seesaw. Where must a girl weighing 25 kgf sit on the other end of the see-saw, so as to balance the boy?

In the diagram shown calculate the resistance (R) offered by the walnut when an effort of 30 N is applied.

The handle of a nutcracker is 16 cm long and a nut is placed 2 cm from its hinge. If a force of 4 kgf is applied at the end of the handle to crack it, what weight, if simply, placed on the nut will crack it?

An effort of 50 kgf is applied at the end of a lever of the second order, which supports a load of 750 kgf, such that the load is at a distance of 0.1 m from the hinge. Find the length of the lever. [Assume that the lever is weightless.]

An effort of 8 kgf is applied on a machine through a distance of 50 cm, when a load of 100 kgf moves through a distance of 3 cm. Calculate

1. velocity ratio
2. mechanical advantage
3. % age efficiency of the machine.

A machine displaces a load of 125 kgf through a distance 0.30 m, when an effort of 12.5 kgf acts through a distance of 4.0 m. Calculate the

1. velocity ratio
2. mechanical advantage
3. % age efficiency of the machine.

Calculate the (a) velocity ratio (b) mechanical advantage (c) % age efficiency of a machine which overcomes a resistance of 800 N through a distance of 0.12 m, when an effort of 160 N acts through a distance of 0.72 m.

A resistance of 500 N is overcome by a machine of V.R. 5 and efficiency 80%. Find (a) mechanical advantage (b) effort required to overcome resistance.

An effort of 500 N is applied through a distance of 0.50 m on a machine, whose efficiency is 90%, such that resistance is overcome through a distance of 0.04 m. Calculate the (a) V.R. (b) M.A. (c) resistance overcome by the machine.

A crowbar of length 2.0 m is used as a machine, to lift a box of 100 kgf by placing a fulcrum at a distance of 0.1 m from the box. Calculate the (a) V.R. (b) effort required. What assumption has been made by you in solving the problem?

A crowbar of length 3 m is pivoted at a point 15 cm from its tip. Calculate (a) mechanical advantage of the crowbar (b) least effort required at its other end to displace a load of 150 kgf.

The handle of a water pump is 90 cm long from its piston rod. If the pivot of handle is at a distance of 15 cm from the piston rod, calculate : (a) mechanical advantage of handle (b) least effort required at its other end to overcome a resistance of 60 kgf.

A crowbar of length 2.5 m is pivoted at a point 25 cm from its tip. Calculate (a) mechanical advantage of crowbar (b) the maximum load displaced by it by applying an effort of 100 kgf on its extreme end.

An almond nut can be broken by applying a force of 2 kgf on the extreme end of the handle of a nutcracker which is 25 cm long. If the nut is placed at a distance of 5 cm from its hinge, calculate the maximum resistance offered by the nut.

A walnut can be broken by applying a direct force of 50 kgf. If the walnut is placed in a nut cracker, the length of whose handle is 18 cm and nut is placed 2 cm from the pivot, calculate the minimum force required to crack the nut.

A key is 5 cm long and turns the levers of a lock at a distance of 1 cm. If the lock is opened by an effort of 10 N, calculate the resistance offered by the levers of the lock.