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(i) Rotating the wheel of a cycle by applying force on the paddle with the help of chain. 

(ii) Lifting a car with a jack. 

(iii) Lifting a bucket full of water from the well using a single fixed pulley

Taking care of machines: Some of the ways in which machines should be cared for are given below : 

1. Machines should be kept in a clean environment, which is free from dust and moisture. 

2. When not in use, machines should be kept covered to prevent collection of dust on them. 

3. Machines made of iron should be protected from rust by coating them with paint. 

4. The moving parts of a machine should be regularly oiled with a good-quality machine oil to reduce friction and wear and tear. The above care of machines increases their life.

Work input is work done on a machine equal to the effort force times the distance through which the force is applied. Work output is work that is done by a machine equals resistance force times the distance through which the force applied. For an ideal machine, the work output is equal to the work input i. e. the efficiency.

Taking care of machines : Some of the ways in which machines should be cared for are given below. 

1. Machines should be kept in a clean environment, which is free from dust and moisture. 

2. When not in use, machines should be kept covered to prevent collection of dust on them. 

3. Machines made of iron should be protected from rust by coating them with paint. 

4. The moving parts of a machine should be regularly oiled with a good-quality machine oil to reduce friction and wear and tear.

It is very difficult to open the sealed metal cap of a cold drink bottle with our bare hands. A simple machine like a bottle opener (Class II lever) multiplies the applied force and much less effort is required to open the cap. Hence, it acts as a force multiplier.

A machine made up of two or more sloping surface is  wedge .

1. False

2. False

3. True

4. False

5. True

6. True

An inclined plane is a rigid sloping surface over which heavy loads can be raised or lowered to a certain height or depth. The mechanical advantage of an inclined plane is the ratio of the length of the plank to the vertical height of the load raised. Its value is greater than one. Therefore, an inclined plane acts as a force multiplier. Thus, it can be used to lift heavy loads. 

Example : If a heavy box needs to be loaded on a lorry, it is far easier to push it over an inclined plane than to lift it up. Steeper the inclined plane, greater will be the effort required to push up the load. Sloping ramps, flyovers, roads on hills and staircases are all examples of inclined planes.

A screw is a simple machine which appears like an inclined plane wound around a rod with a pointed tip.

 Examples : ajar lid, a drill.

The wheel and axle is a simple machine having a wheel and an axle. The linear motion of axle is obtained by rotating the wheel so as to reduce friction. 

Example: Steering wheel, screw drivers, water tap etc.

Pedals of the bicycle are connected to the wheels through the axle, when the axle starts rotating, the wheels also start rotating.

1. Machines, simple or complex, are used to get more work done in less time and with less effort.

2. Machines are used to accomplish certain tasks more easily.

3. Use of simple or complex machines depends upon the task to be carried out and the time and the efforts required to do it.

1. Lever is a simple machine made up of 3 parts : Load, effort and fulcrum. 

2. Order of the lever are determined on the position of the effort, the fulcrum and the load.

1. Machines which have only one or two parts and a simple and easy structure are simple machines. 

2. Example : the bottle opener, nail cutter. 

3. Simple machines can be handled easily. 

4. We use many simple machines in our day to day life.

1. Complex machines have many parts which carry out many processes for completing a task. 

2. For this purpose the parts are joined to one another. 

3. Therefore, these machines are called complex machines. 

4. Some of the parts of such complex machines are actually simple machines. 

5. The structure of complex machine is complicated.

Some machines have many parts and they carry out many processes for completing a task. 

For this purpose,

The parts are joined to each other. 

They are called complex machines.

Levers : 

1. See – saw – lever of the first order. 

Load – fulcrum – effort. 

2. Wheelbarrow – lever of the second order. 

Fulcrum – load – effort. 

3. Lemon squeezers – lever of the second order. 

Fulcrum – load – effort. 

4. Tongs – lever of the third order. 

Fulcrum – effort – load.