2.6 effect of the force

8/6/2019 2.6 Effect of the Force

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2.5 Understanding the Effects of a

Force

Prepared by N M Solehin


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WHAT IS FORCE?

A force is a push or a pull.

It has strength ormagnitude.

It has direction.Force is a vector quantity.


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Lets listen to the Force

song..

And enjoy the next video


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RELATIONSHIP BETWEEN

MASS & ACCELERATION.

Experiment

Result

video1

video2

CONSTANT FORCE


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RELATIONSHIP BETWEEN

FORCE & ACCELERATION.

Experiment

Result

video1

video2

CONSTANT MASS


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The Derivation ofF=ma

it is found that;

1) a w F when m (mass) is constant.

2) a w 1/m when F (force) is constant.

Combine 1) & 2):

a w F/m

Arrange a w F/m,

we get : FwmaAnd,F= kma

where k=constant = 1

Therefore,F= ma **Unit ofForce is Newton


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1. What force is needed so that an object with mass of

3 kg has an acceleration of2 m s-2?

TEST YOURSELF.

Force = mass x acceleration

= 3 kg x 2m s-2

= 6 kgm s-2 or Newton

2. If a force F is applied to a wooden box of mass 2 kg, it

moves with an acceleration of3 m s-2. Find the acceleration

of another box of6 kg if the same force is applied to it.

For the 1st box

Force = 2 kg x 3 m s-2

= 6 Newton

Applying F=ma again,

a = F/m

= 6/6

= 1m s-2


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THE EFFECTS OF A FORCE.

Change the shape of an object.


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Other example

A straight ruler forms

an arc when bending

forces are applied to

both ends. The forces

can change the shape

of an object.


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THE EFFECTS OF A FORCE.

Change the original state of

motion (rest or moving).

-stop a moving object

-change direction of moving object-move a stationary object


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When the forces acting on an object are balanced,

they cancel each other out

The resultant or net force, Fnet = ma = 0

a = 0 m s

Object at rest(v = 0 m s)

Object in motion(v 0 m s)

Stay at restStay moving with constant velocity


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BALANCED FORCE.

Stationary object

weight,w= mg

Normalreaction, NMagnitude N = W but R

acts in an opposite

direction to the weight.

( object is in equilibrium )


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BALANCED FORCE.

weight,w= mg

Normalreaction, N

Force, FFrictional force

Force , F = Friction

Resultant = F Friction

= 0

(object is inequilibrium)

Examples :

1.A

car

move at constantvelocity.

2.A plane flying at

constant velocity.


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UNBALANCED FORCE.

Fnet

The force, F is greater

than the frictional force, Fr

acting on the bicycle.

The resultant force, Fnet

causes the bicycle to

accelerate forward.

Fnet = F Ffriction = ma

FFr


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The answer is D


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Fnet = Fapplied Ffriction = ma

change the size orshape of an object

The effectsof forces

start or stopmoving object

change thedirection of

a moving object

move a stationaryobject

change thevelocity of a

moving objectslow down a moving

object

2.6 effect of the force

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