class 9 practice sheet work and energy
CLASS IX
CH.
WORK & ENERGY
1. Two balls of masses m each
are raised to a height h and 2h respectively.
What will be the ratio of their potential energies?
2. A ball of mass 2kg is
thrown up at a speed of 10m/s. Find the kinetic energy of the ball at the time
of throwing. Also, find the potential energy of the ball at the highest point.
3. Two objects are kept at different heights, first object is at
5m and second object is placed at 15 m. Which object has more Potential energy
if the first object is 5 times heavier than the second?
4. An object with 100 N weights is raised to a
height of 15m. Find the potential energy possessed by the object at that
height. Also, find the new potential energy:
a. If the same object is raised half of its original height.
b. If the same object is raised to three times its original height?
5. The following
data was obtained for a body of mass 1 kg dropped from a height of 5 m:
|
Distance
above ground |
Velocity |
|
5
m |
0
m/s |
Show by
calculations that the above data verifies the law of conservation of energy
(Neglect air resistance). (g = 10 m/s2).
6. A lamp consumes 500 J of electrical energy
in 20 sec. What is the power of the lamp?
7. Calculate the power of a crane in watts,
which lifts a mass of 100 kg to a height of 10 m in 20s.
8. Calculate the electrical energy consumed in
Joules if a toaster of 60 W is used for 30 minutes.
9. A
man weighing 500 N carried a load of 100 N up a flight of stairs having 20
steps each of 0.5 m high in 50 seconds. Calculate his power?
10. A
car of weight 20000 N climbs up a hill at a steady speed of 8 m/s, gaining a height of 120 m is 100 s.
Calculate :
(a) work done by the car.
(b) power of engine of car.
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