EACH QUESTION 2 MARK EACH
Question 1. A dog weighing 25 kg, while chasing a cat, jumps over a fence of height 1.6
m. What is the potential energy of dog at the top of fence ?
(Take gravity due to earth 'g'=10 m si)
Question 2. In a construction site, a crane lifts 1000 kg of concrete mix to roof top at a
height of 20 meters in 50 seconds. If the value of gravity 'g' due to earth is 10 m s, the
power of elevator will be.
Question 3. Calculate the power of an electric motor that can lift 800 kg of water to store in a
tank at a height of 1500cm in 20s. (g=10m/s).
Question 4. Calculate the electricity bill amount for a month of 30 days, if the following devices
are used as specified:
a.Iwo bulbs of 40W for six hours.
b.two tubelights of 50W for eight hours
C.A TV of 120W for six hours.
d. Give the rate of electricity is 2.50 rupees per unit?
Question 5.Calculate the energy posses by a stone of mass 10kg kept at a height of 5m If 196x10^2 1 of
energy were used to raise a 40kg boy above the ground, how high would he be raised?
Answers
Answer:
answer 1)
Mass of the dog= m=25 kg
Height of fence= h= 1.6 m
Acceleration due to gravity=g=10 m/s²
∴Potential energy of dog= m.g.h
= 25×10×1.6
= 25×16
= 400 kgm²/s²
= 400 J
answer 2 :
here m= 100kg
h= 10m
t= 20s
g= 10m/s square
g= 10 m/ s square
the. Power of crane is
p= mgh/t
100×10×10/20= 10000/20
= 500w
answer 3:
The power is defined as
Here W is the work done and t is the time taken.
The work done by motor to lift water,
W = mgh
Here, m is the mass and h is the height.
Given m= 800 kg, h = 1500 cm = 15 m, g = 10 m/s^2 and t = 20 s.
substitute the values in work done formula, we get
W = 800 kg x 15 m x 10 m/s^2
W = 120000 J.
Therefore, power is
P = 6000 W.
answer 4 :
Energy used by :-
Bulb = 0.04 X 2 X 6 = 0.48 units
Tube lights = 0.05 X 2 X 8 = 0.8 units
TV = 0.12 X 6 = 0.72
Total energy consumed = 0.48 + 0.8 + 0.72 = 2 units
Bill amount = 2.50 X 2 X 30 = rs.150
answer 5 )
Explanation:
Answer:
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