Page 149 - Active Science 5 Ebook and Activity

Anything with a sharp edge and a blunt edge is a wedge. Blades, axes, teeth, knives,
etc., are other examples of a wedge.

Let’s Recapitulate

Define the following.

1. Simple machine 2. Screw
3. Lever 4. Wheel and axle
5. Inclined plane

Pulley

This simple machine is made up of a wheel and a rope. A pulley helps us to lift heavy
loads. It makes our work easier by changing the direction in which the force has to be

applied.

Thus in a pulley, the effort is applied in one direction and the load is lifted in the other
direction. For example, it is difficult to lift a bucket full of water by the pull of a rope
vertically. But with the help of a pulley, the bucket can be easily lifted as force is applied
in downward direction. Pulleys are used to hoist a flag, to draw water from a well, etc.

These are also used in a crane at a construction site.

Pulley

Load
Pulley Force
pulling
rope

LET’S
REVISE Let’s Pronounce Together

• There are four types of forces: gravitational, electrostatic, gravitational electrostatic

frictional and magnetic force. frictional kinetic
• Energy is the capacity to do work. fulcrum forceps

• In a lever, the object to be moved is called load. The force inclined pulley
used to lift the load is effort, and the fixed point on which the wedge
rod moves is ctalled a fulcrum.

• Depending upon the position of load, effort and fulcrum, there are 3 types of levers: lever
of first class (fulcrum is in the centre); lever of the second class (load is in the centre); and
lever of the third class (effort is in the centre).

• A heavy load can be easily lifted up to a height with the help of an inclined plane.

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Active Science-5