Question

A man weight 60kg climbs up a stair case with a a 20 kg load on his head. the stair case has 20 steps and each step has a height 20 cm. The Increase in potential energy of the man is (g=10 ms^-2)​

Answer 1

Given:-

• Mass of man = 60kg

• Mass of load = 20kg

• No. of steps = 20

• Height of each steps = 20cm → 0.2m

• Acceleration due to gravity = 10m/s²

To Find:-

• The Increase in Potential energy

Formulae used:-

• P. E = mgh

Now,

→ Total Mass = Mass of man + Mass of load

→ Total Mass = 60 + 20 → 80kg

→ No. of stairs = 20

→ Height of 20 Stairs = 20 × 0.2 → 4m

Therefore,

→ Potential energy = mgh

→ P. E = 80 × 10 × 4

→ P. E = 800 × 4

→ P. E = 3200J

Hence, The Increase in Potential Energy is 3200J.

Answer 2

Explanation:

Given : -

• Mass of man = 60kg

• a 20 kg load on his head.

• the stair case has 20 steps and each step has a height 20 cm.

Solution : -

Mass of the man while he was climbing = 60 + 20= 80 kg

Height of the stair case = No. of steps × height of one step

= 20 × 20

= 4 m

F = m× g ( acceleration due to gravity)

= 80 × 10

= 800 N

Workdone = Force × height

= 800 × 4

= 3200 Joule