MEDIUM
9th CBSE
IMPORTANT
Earn 100

An old man does 200 J of work in 10 s and a young man does 100 J of work in 4 s. (i) Who is delivering more power? (ii) Find the ratio of the power delivered by the old man to that delivered by the young man.

Important Questions on Work and Energy

MEDIUM
9th CBSE
IMPORTANT
Physics For Class 9>Chapter 4 - Work and Energy>Exercise>Q 5

Determine the power of an engine required to lift 100000 kg of coal per hour from a mine which is 360 m deep. (g = 10 m/s2)

MEDIUM
9th CBSE
IMPORTANT
Physics For Class 9>Chapter 4 - Work and Energy>Exercise>Q 6
The engine of a train has to apply a force of 5000 N to overcome friction to run at a uniform rate of 90 km/h. What is the power developed by the engine?
EASY
9th CBSE
IMPORTANT
Physics For Class 9>Chapter 4 - Work and Energy>Exercise>Q 7
If an electric bulb of 100 W is lighted for 5 hours, how much units of energy would be consumed?
MEDIUM
9th CBSE
IMPORTANT
Physics For Class 9>Chapter 4 - Work and Energy>Exercise>Q 8
An electric bulb consumes 7.2 kJ of electrical energy in 2 minutes. What is the power of the electric bulb?
MEDIUM
9th CBSE
IMPORTANT
Physics For Class 9>Chapter 4 - Work and Energy>Exercise>Q 9
A man of mass 60 kg climbs stairs of total length 20 m in 2 minutes. Find the power delivered by the man. (g = 10 m/s2)
MEDIUM
9th CBSE
IMPORTANT
Physics For Class 9>Chapter 4 - Work and Energy>Exercise>Q 10
The work done by the heart is 1 J per beat. Find the power of the heart if it beats 72 times per minute.
MEDIUM
9th CBSE
IMPORTANT
Physics For Class 9>Chapter 4 - Work and Energy>Exercise>Q 11
Two girls A and B each of weight 400 N, climb up a tree of a height of 8 m. Girl A takes 20 s while B takes 50 s to accomplish this task. What is the power expended by each girl?
EASY
9th CBSE
IMPORTANT
Physics For Class 9>Chapter 4 - Work and Energy>Exercise>Q 12
A certain household consumes 650 units of electricity in a month. How much is this electricity in joule?