Chapter - Work , Energy and Machines

 Exercises

1. When is work done by a force ?

Answer-Work is done by a force  when the point of application of a force moves through a distance.

2. Name two things which store chemical energy.

Answer -Food and fuels store chemical energy.

3. Name three forms of energy.

Answer- Three forms of energy - Solar energy, Chemical energy and Electrical energy.

4.Define a Machine.

Answer-A machine is a device through which of force applied at a point over comes resistance some other point.

5.Name four categories of machine

Answer-Four categories of machine - 1. Lever 2. Wedge 3. Screw 4. Wheel and axle

6.What is a Lever ? What is it's fulcrum?

Answer - A Lever is a rigid body capable of rotating about a point on itself .The fulcrum of a lever is the point about which can rotate.

7.What is load and effort in the context of a Machine?

Answer - The effort is the force applied to a machine and the load is the resistance overcome by a machine.

8.What is the basis on which levers are divided into the classes?

Answer - There are 3 classes of levers. A class one lever has the fulcrum in the middle class two lever has load in the middle and a class three lever has effort in the middle.

9.Define the mechanical advantage.

Answer-The mechanical advantage of a machine is defined as the ratio of the load to the effort.

10. What is a force multiplier?

Answer - A force multiplier is a simple machine which multiplies the effort.