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Matter In Our Surroundings

Question
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Two girls each of weight 400 N climb up a rope through a height of 8 m. We name one of the girls as A and the other as B. Girl A takes 20 seconds while B takes 50 seconds to accomplish this task. What is the power expended by each girl?

Solution
(i)  Case 1: Girl A

Given,

Weight of the girl, mg  = 400  N

Height which girl A climbs up, h = 8 m

Time taken, t= 20 s

So, power expended by girl A, P is given by, 

Work donetime taken = mght = 400×820 = 160 W

(ii) Case 2: Girl B 

Given, 

Weight of the girl, mg = 400 N

Height which girl B climbs up, h =  8  m

Time taken, t=  50 s

Power expended by girl B is given by, 

P = Work donetime taken = mght= 400×850 = 64 W 

Some More Questions From Matter In Our Surroundings Chapter

Convert the following temperature to Celsius scale.

300K

Convert the following temperature to Celsius scale.

573 K

Convert the following temperatures to Kelvin scale

25°C

What is the physical state of water at

100 °C

For any substance, why does the temperature remain constant during the change of state ?

Suggest a method to liquify atmospheric gases.

Convert the following temperatures to Kelvin scale.

35°C

Give reason for the following observations.

Naphthalene balls disappear with time without leaving any solid.

Give reason for the following observations.

We can get the smell of perfume sitting several metres away.

What is the physical state of water at

a) 25°C
b)00C
c)1000C

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