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# Force

We do so many activities in our daily life like, opening a door, kicking a football, striking a carrom coin etc. , To do these activities an external agency is needed.

Force

We do so many activities in our daily life like, opening a door, kicking a football, striking a carrom coin etc. , To do these activities an external agency is needed. This external agency is called force. Force can either set an object at rest into motion or bring a moving object to rest. It can even change the shape and size of certain objects.

Force is defined as an external agency which changes or tends to change the state of rest or the state of uniform motion of a body or the direction of a moving body or the shape of a body. Force is a vector quantity, which has magnitude and direction. It is measured by a unit called 'newton' (N).

Effects of Force

Observe the strokes a batsman in cricket game. If he wants to hit the cricket ball to the boundary, the striking force on the ball must be greater. So, the greater the force you apply on a body, greater will be its effect on it.

Activity 1

Fix a matrix of sharp pins on a wooden board in rows and columns. Take a big blown up balloon. Place it gently over the pins and place a small book on the top of the balloon. Will the balloon burst? Will the pins prick the balloon?

Aim : To understand the effect of a force depends on the magnitude of the force and the area over which it acts.

Materials required : Sharp pins, wooden board, balloon.

Procedure :

(i) Fix a matrix of sharp pins on a wooden board in rows and columns.

(ii) Take a big blown up balloon.

(iii) Place it gently over the pins.

(iv) Place a small book on the top of the balloon.

(v) Observe what happens?

(vi) Will the balloon burst? Will the pins prick the balloon?

Inference :

(i) The balloon will not burst. If you prick the balloon with a single pin it will burst. But this did not happen even though many more pins were pricking the balloon.

(ii) A single pin produces a large pressure over a small area. But, when a large number of pins prick a body, each pin exerts very little pressure on the balloon, as the applied force gets distributed over a large surface of the body. So, the balloon will not burst.

Conclusion: We conclude that the effect of a force depends on the magnitude of the force and the area over which it acts.

If you prick a blown up balloon with a single pin it will burst. But, this did not happen even though many more pins were pricking the balloon. A single pin produces a large pressure over a small area. But, when large number of pins prick a body, each pin exerts very little pressure on the balloon, as the applied force gets distributed over a large surface of the body. So, the balloon will not burst.

Thus, we can conclude that the effect of a force depends on the magnitude of the force and the area over which it acts. The force acting perpendicularly on any given surface area of a body is known as thrust. It is measured by the unit newton.

Tags : Chapter 2 | 8th Science , 8th Science : Chapter 2 : Force and Pressure
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8th Science : Chapter 2 : Force and Pressure : Force | Chapter 2 | 8th Science