IX M SAII WORK ENERGY SURFACE AREA

            

1.     [1]A cycle together with its rider weighs 100 kg. How much work is needed to set it moving at 3 m/s?

2.       [1]What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.

3.       [1]A man performs 270 J of work in 9 s. Calculate the power.

4.       [1]Calculate the speed of a body of mass 20 g having a kinetic energy of 10 J.

5.       [1]Convert 1kWh into joules.

6.       [1]How much work is done at the rate of 40 W in 40 s?

7.       [2]A 1000-W heater is used for 2 hour every day for 30 days. Find the cost of electricity if the rate is Rs 8.00/unit.

8.       [2]A body of mass 25 g has a momentum of 0.40 kg m/s. Find its kinetic energy.

9.       [2]Find the expression for the gravitational potential energy of a body of mass m at a height h.

10.   [2]Find the expression for kinetic energy of a body of mass m moving at a speed v.

11.   [2]A boy of mass 50 kg runs up a staircase of 25 steps in 10 s. If the height of each step is 15 cm, find his power. Take g = 10 m s^–2.

12.   [2]Calculate the work required to be done to stop a car of 1200 kg moving at a velocity of 60 km/h?

13.   [2]What is the work to be done to increase the velocity of a car from 2m/s to 5 m/s if the mass of the car is 2000 kg?

14.   [3]Harish has built a cubical water tank wit lid for his house, with each outer edge 1.5 m long. He gets the outer surface of the tank excluding the base, covered with square tiles of side 25 cm. Find how much he would spend for the tiles, if the cost of the tiles is Rs 600 per dozen.

15.   [3]The floor of a rectangular hall has a perimeter 250 m. If the cost of painting the four walls at the rate of Rs 10 per m² is Rs 15000, find the height of the hall.

16.   [3]A small indoor greenhouse (herbarium) is made entirely of glass panes (including base) held together with tape. It is 30 cm long, 25 cm wide and 25 cm high.

(i) What is the area of the glass?

(ii) How much of tape is needed for all the 12 edges?

17.   [3]A village, having a population of 4000, requires 150 litres of water per head per day. It has a tank measuring 20 m × 15 m × 6 m. For how many days will the water of this tank last?

18.   [3]A river 3 m deep and 40 m wide is flowing at the rate of 2 km per hour. How much water will fall into the sea in a minute?