Question

If we lift a body 7 kg vertically upwards to a height of 10 m, calculate the work done

in lifting the body. ​

Answer 1

Given :-

Mass of the body = 7 kg

Height the body is carried upwards = 10 m

To Find :-

The work done in lifting the body.

Analysis :-

Here we are given with the mass and height of the body.

In order to find the work done substitute the values in the questions such that work done is equal to mass into gravity into height.

Solution :-

We know that,

• m = Mass
• h = Height
• g = Gravity
• w = Work done

Using the formula,

$\underline{\boxed{\sf Work \ done=Mass \times Gravity \times Height}}$

Given that,

Mass (m) = 7 kg

Gravity (g) = 10 m/s

Height (h) = 10 m

Substituting their values,

⇒ w = mgh

⇒ w = 7 × 10 × 10

⇒ w = 7 × 100

⇒ w = 700 J

Therefore, the work done in lifting the body is 700 J.

Answer 2

Answer :

Work done in lifting the body is 686 kJ

Explanation :

To Find,

• The work done on lifting the body

Solution,

Given that,

• Mass of the body = 7 kg
• Height from the level of the ground = 10 m

As we know that,

Work done = Potential energy

★ Potential energy = m × g × h

Where,

• m = Mass
• g = acceleration due to gravity and it's value is 9.8 m s·²
• h = height

Therefore,

» 7 × 9.8 × 10

» 68.6 × 10

» 686

∴ Potential energy or Work done in lifting the body is 686 kJ

More Information

• The S.I. unit of work is Joule.
• Kinetic energy = 1/2 mv²
• Weight = m × g
• Potential energy = m × g × h
• The S.I. unit of power is watt.