Question

The work done in lifting a 10 kg load of bricks to the top of a building 20 m hight is ( g = 9.8 ms-2 )

Explation
10×20=200
200×9.8 =1960 J
Answer is
1960 J​

Answer 1

Good! answer is given by you already. But, while writing this method in exam, the verifier may not give you full marks for this answer.

We have,

Mass of load = 10 kg

Height = 20 m

Acceleration due to gravity = 9.8 m/s²

We know,

$\boxed{E_p \ or \ PE = mgh}$ (gravitational potential energy)

∴ PE = (10 kg)(9.8 m/s²)(20 m)

⇒ PE = 98 × 20 Nm

⇒ PE = 1960 J or 1.96 kJ (answer).

More:-

• Potential energy is the energy possessed by an object due to the virtue of it's configuration or position.
• In the above answer, we used the concept of gravitational potential energy. There are some kinds of potential energy like the elastic potential energy.

Which is given by,

$\boxed{E_{elastic} = \frac{1}{2}kx^2}$ (in usual terms).

Answer 2

$\bold{Answer\;:-}$

Given :-

• Mass of the load of bricks, m = 10 kg

• Height of the building, h = 20 m

• Acceleration due to gravity, g = 9.8 m/s²

To find :-

• The work done in lifting a load of bricks, W = ?

Formula :-

• Potential energy = Mass of the body × Acceleration due to gravity × Height to which it is raised

• P.E = m*g*h ( gravitational potential energy because it is under the influence of gravity )

Solution :-

• PE = 10 × 9.8 × 20

• PE = 1960 J

• PE = 1.9 kJ

Extra :-

• The above answer mentioned about the spring potential energy / elastic potential energy which is ½kx². Work done on a spring or potential energy of a spring stretched through a distance x, W = U = ½kx². For the spring potential energy ½kx², the zero of the potential energy is the equilibrium position of the oscillating mass.

• Potential energy : The notion of potential energy applies to only those forces where the work done against the force get stored up as energy by virtue of position or configuration of the body. When external constraints are removed this energy appears as kinetic energy.

• For the gravitational potential energy, the zero of potential energy is chosen to be ground.

• Every every mechanical energy is not associated with potential energy. The work done by friction over a closed path is not zero because no potential energy can be associated with friction.

$\bold{Hope\;it \; helps\;!}$