Download Winter Vacation Home Work -Science-

Holiday Homework
Class -X
*Prepare power point presentation of ray diagrams.
Holiday Homework (Class -9)
1.
2.
Find the work done when a force of 15 N, moves a body by 5 m in its own direction.
75 J.
A porter lifts a luggage of 15 kg from the ground and puts on his head 1.5 m above the ground. Calculate the
work done by him on the luggage.
75 J.
3.
Calculate the work done in lifting 200 kg of water through a vertical height of 6 meter. (g = 10 m/s2).
12,000 J.
4.
A car weighing 1000 kg and travelling at 30 m/s stops at a distance of 50 m, decelerating uniformly. What is the
force exerted on it by the brakes? What is the work done by the brakes?
-9000 N, -4,50,000 N.
5.
A mass of 10 kg is at a point A on a table. It is moved to a point B. If the time joining A and B is horizontal, what
is the work done on the object by the force of gravity? Explain your answer.
0.
6.
A toy car is pulled by a force of 5 N at an angle of 60˚ horizontally. If distance covered is 2 meters, find the work
done.
5 J.
7.
What is the work to be done to increase the speed of a car from a 54 km/h to 90 km/h if the mass of the car is
1200 kg? 24,0000 J.
8.
9.
A body is moving with a speed of 10 m/s. I mass of the body is 2 kg, find its kinetic energy. 100 J.
Suppose a hammer falls freely on nail placed on piece of wood has a mass of 1 kg. If it falls from a height of 1 m.
How much kinetic energy will it have just before hitting the nail? (g = 10 m/s2).
10 J.
10. A car is moving with a uniform velocity of 54 km/h.
What is the Kinetic energy of a boy of a mass 40 kg sitting in the car? 4500 J.
Suppose the car is moving with uniform velocities 18 km/h, 36 km/h, 54 km/hr, and 72 km/hr at some
interval of time.
500 J, 2000 J, 4500 J, 8000 J.
(iii) Plot a graph between a kinetic energy and the velocity. What is the nature of the curve?
(i)
(ii)
11. A bag of wheat weighs 200 kg. To what height it should be raised so that its potential energy may be 9800 J? (g =
9.8 m/s2).
5 m.
12. If a man 75 kg climbed a staircase upto a vertical height of 6 m. How much potential energy stored in his body?
G= 10 m/s2.
4500 J.
13. If acceleration due to gravity is 10 m/s2, what will be the potential energy of a body of mass 1 kg kept at a height
of 5 m?
50 J.
14. Potential energy of a body of a mass 5 kg is 15 J relative to the ground. Find its height? (g = 10 m/s2).
0.3 m.
15. A body of mass 2 kg is thrown vertically upwards with an initial velocity of 20 m/s. What will be its potential
energy at maximum height? (g=10 m/s2).
400 J.
16. S is instructed to carry an important package from the base camp at B to summit a of a hill at a height of 1200
m. S weighs 800 N and the package weighs 200 N.
(i) How much work does s do against gravity?
(ii) What is the potential energy of the package at A if it is assumed to be zero at B?
12 x 105 J, 2.4 x 105 J.
17. A boy weighing 50 kg climbs up a vertical height of 100 m. Calculate the amount of work done by him. How much
potential energy does he gain? (g = 9.8 m/s2).
49000 J.
18. A load of 100 lg is pulled up by 5 m. Calculate the work done. 4900 J.
19. A person of mass 50 kg climbs a tower of height 72 meter. Calculate the work done. 35280 J.
20. A ball of mass 200 gm falls from a height of 5 meters. What is its Kinetic energy when it just reaches the ground?
9.8 J.
21. A ball of mass 0.5 kg slows down from a speed of 5 m/s to that of 3 m/s. Calculate the change of kinetic energy
of the ball. State your answer giving proper units.
4 J.
22. Calculate amount of work done, when a body of mass 10 kg is lifted vertically up to a height 3 m. Take g = 9.8
m/s2, also calculate its potential energy. If it’s dropped, then what will be its kinetic energy just before reaching
the ground?
294 J, 294 J, 294 J.
23. A man whose mass is 50 kg, climbs up 30 steps of the stairs in 30 seconds. If each step is 20 cm high, calculate
the power used in climbing the stairs.
100 watt.
24. If an electric bulb of 100 watt is lighted for 2 hr how much electric energy would be consumed?
0.2 kw-hr.
25. A woman pulls a bucket of water of total mass 5 kg from a well which is 10 m deep in 10 seconds. Calculate the
power used by her.
50 watt.
26. A pump delivers 1000 litres of water in a tank at a height of 15 metres in 120 sec. Find work done by the pump
and its power.
(g = 10 m/s2 and 1 liter = 1 kg).
1.25 kW.
27. A certain household has consumed 250 units of energy during a month. How much energy is this in joules?
9 x 108 J.
28. An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is
allowed to fall, find its Kinetic energy half way down.
1000 J.
29. An electric heater is raised 1500 W. How much energy does it use in 10 hr?
15 units.
30. Calculate power of a body which does 10 J of work in 2 seconds.
10,000 J, 83.33.
31. A man weighing 80 kg carries a suitcase of mass 20 kg to second floor of a building 10 meter high in 2 minute.
Calculate the work done by him and the power.
833.33 watt.
32. A pump fills a tank of capacity 100 litres in 5 minutes. If tank is situated at a height of 25 metres from the
ground, find power of the pump.
(g = 10 m/s2).
*Prepare power point presentation of work, power and
energy.