A girl of mass 40 kg runs up a staircase of 30 steps in 10 s. If the height of each step is 0.1 m, find the power developed by her. Take g = 10
Answers
Answer:
ANSWER EXPLANATION: Think of the equation as an equation for a line
y=mx+b
where in this case
C=
5
9
(F−32)
or
C=
5
9
F−
5
9
(32)
You can see the slope of the graph is
5
9
, which means that for an increase of 1 degree Fahrenheit, the increase is
5
9
of 1 degree Celsius.
C=
5
9
(F)
C=
5
9
(1)=
5
9
Therefore, statement I is true. This is the equivalent to saying that an increase of 1 degree Celsius is equal to an increase of
9
5
degrees Fahrenheit.
C=
5
9
(F)
1=
5
9
(F)
(F)=
9
5
Since
9
5
= 1.8, statement II is true.
The only answer that has both statement I and statement II as true is D, but if you have time and want to be absolutely thorough, you can also check to see if statement III (an increase of
5
9
degree Fahrenheit is equal to a temperature increase of 1 degree Celsius) is true:
C=
5
9
(F)
C=
5
9
(
5
9
)
C=
25
81
(whichis≠1)
An increase of
5
9
degree Fahrenheit leads to an increase of
25
81
, not 1 degree, Celsius, and so Statement III is not true.
The final answer is D.
Given:
A girl of mass 40 kg runs up a staircase of 30 steps in 10 s
To find:
the power developed by the girl
Solution:
It is given that the girl is climbing the stairs so the work done by the girl will be given by:
Work = mgh
where
m = 40 kg
g = 10 m/sec²
h = 0.1 × 30 = 3 m
Work = 40×10×3
Work = 1200 joules
and the power developed by the girl is given by:
Power = work/time
Work = 1200 J
Time = 10 sec
Power = 1200/10
Power = 120 Watt