Question

A roller weighing 1 tonne is being dragged along a road.What is the work done against gravity?Why?

Answer 1

Answer:

Given:

A roller weighs 1 tonne = 1000 kg.

It is dragged along a road.

To find:

Work done against gravity

Concept:

Work done is a Scalar Quantity.

It is given by the dot product (Scalar product) of force vector and displacement vector.

Work = F . d

=> Work = F × d × cos(θ),

where θ is the angle between force and displacement.

Now when the roller is dragged along the road, the displacement vector is along the road.

But the force vector (gravity) is vertically downwards.

So angle between them = θ = 90°

Calculation:

Work = F × d × cos(90°)

=> Work = 0 Joules.

Answer 2

Given :----

• weight of roller = 1 ton dragged along a road.

To Find :-----

• work done against Gravity ?

Concept used :----

• When we lift a body in perpendicular direction, the work is said to be done against gravitational force.
• value of cos90°(Perpendicular Direction b/w Force & Displacement) = 0 .
• Also in this case their will be no Displacement in the direction of Force .
• work done = Force × displacement × cos@ .

Solution :----

Work done = F × D × cos@

→ work done = F × D × cos90°

→ work done = F × D × 0

→ work done = 0 Joules .

So, we can say that ,,

→ if an object is moving in horizontal direction on the surface of earth, then work done by gravity is ‘zero’.

(Hope it Helps you)