Question

calculate w when F = 20N , d = 3m and theta = 60° is given
$\bf\red{urgent}$
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Answer 1

Answer:

30 Joule

Explanation:

GIVEN

Force acting on the body (F) = 20N

The displacement occurred (S) = 3m

Angle between direction of force and displacement of the body (θ) = 60°

TO FIND : Work done by the force.

FORMULA TO BE USED

$w = f \times s \times cos \theta$

where θ is the angle between S and F.

Value of Cos θ at different values.

When θ = 0° , Cosθ = 1

When θ = 30° , Cosθ = √3/2

When θ = 45° , Cosθ = 1/√2

When θ = 60° , Cosθ = 1/2

When θ = 90° , Cosθ = 0

SOLUTION

W = F × S × Cosθ

= 20 × 3 × Cos60° [ θ = 60° (given)]

= 20 × 3 × 1/2 [ According to value of Cosine angle]

= 10 × 3

= 30J (ANS)

SPECIAL CASES:-

When θ = 0, [Parallel]

W = F × S

When θ = 90° [Perpendicular]

W = 0 Joule

When θ = 180° [Anti-Parallel]

W = -F × S

Answer 2

:)In this case force will be taken as Fscos∅.But why?

Reason:-there are two component of force F which are acting the object.One is Fcos∅ and the other is Fsin∅.

Fcos∅ is only responsible for the movement of the object upto distance of 3m because Fsin∅ acts in upward direction .

And we always cosinder that force which is responsible for the movement of the object.

So, neglecting Fsin∅(as it is not responsible for the movement of object) we can say

work done=responsible force×distance travelled

=>Fcos∅×s=Fscos∅

Solution:-

Work done =20×3cos60°=60×1/2=30j