Question

How much mechanical work is done in:

a. lifting a 2 – kg brick to a height of 1 m?

b. holding the brick 1 m above the floor?

c. slowly moving the brick a horizontal distance of 1 m?

d. letting the brick fall a distance of 1 m?

Answer 1

a. A 2 – kg brick lifted to a height of 1 m.

• When the block is being lifted, the work done will be equal to the potential energy gained by the object.

W = m × g × h

=> W = 2 × 10 × 1

=> W = 20 Joules.

b. Holding the brick 1 m above the floor.

• The work done to hold an object at a height will be zero because no potential energy is gained/lose.

c. Slowly moving the brick a horizontal distance of 1 m.

• The work done will be zero.

• This is because , the force and displacement vector are at right angles (90°) to one another.

d. Letting the brick fall a distance of 1 m.

• The work done will be again -20 J (opposite to work done while lifting the block to that height).

$\star$ Hope It Helps.