Page 40 - Science Class 6 Times Publication

Main Points to Remember

1. The simple devices which make our work easier and faster
are called simple machines.

2. The simple machines can be categorized into six types:
pulley, wheel and axle, inclined plane, screw and wedge.
3. A long rigid bar that is capable of moving about a  xed
point is called lever.
4. A lever may be- rst class lever, second class lever or third

class lever.

5. A pulley is a round metallic or wooden disc with a grooved rim .
6. Wheel and axle consists of a large cylinder  xed rigidly with
a small cylinder. The large cylinder is called wheel and the
small cylinder is called axle.
7. A slanted surface over which load can be pulled or pushed is
called inclined plane.
8. A wedge is a simple machine which has a sharp part at one
end and at part at other end.

Exercise

1. Choose the best alternative in each case:

a. The xed point about which a lever rotates is called

i. Load ii. Effort
iii. Fulcrum iv. Mechanical advantage

b. Which of the following is a rst class lever?

i. Broom ii. Nut-cracker
iii. Nail-cutter iv. None of these

c. Winding road in a hill
i. Pulley ii. Inclined plane

iii. Wheel and axle iv. Screw

Times' Crucial Science and Environment 36 Book 6