Model Test Paper മാതൃകാ ചോദ്യപേപ്പർ
A full paper in the Kerala Class 9 Physics pattern for this chapter, covering the whole of “Work and Energy” – work and the joule, work against gravity, positive and negative work, energy and its forms, potential and kinetic energy, energy transformation and conservation, hydroelectric power, and power. Most numericals need careful units (minutes, km/h, kcal). Work on paper with a timer before you look at the solutions.
Standard IX · Physics
Chapter 6 · പ്രവൃത്തിയും ഊർജവും · Work and Energy
- The first 15 minutes are cool-off time: read every question and plan your answers; do not write.
- Answer all questions. Marks for each question are shown on the right.
- For numericals write Given → Formula → Substitution → Answer with the unit. Use the value of g given in each question.
- 1 HP = 746 W; 1 kcal = 4200 J.
SECTION AAnswer all · 8 × 1 = 8 marks
1.
When a force of 1 N moves an object through 1 m in the direction of the force, the work done is .
(1)2.
Which of the following is a scalar quantity?
(1)(a) force(b) displacement(c) velocity(d) energy
3.
A headload worker stands still for 5 minutes holding a 20 kg sack on his head. The work done by him on the sack during this time is
(1)(a) 0 J(b) 200 J(c) 1000 J(d) 6000 J
4.
Find the relation and fill in: kinetic energy : ½mv2 :: potential energy due to position :
(1)5.
A stone is thrown vertically upwards. While it rises, the work done on it by the force of gravity is
(1)(a) positive(b) negative(c) zero(d) equal to its kinetic energy at the top
6.
1 HP = W
(1)7.
The energy stored in a compressed spring is
(1)(a) kinetic energy(b) potential energy due to position(c) potential energy due to configuration(d) heat energy
8.
The unit of power is named after the Scottish scientist , who built a much more efficient steam engine.
(1)SECTION BAnswer all · 5 × 2 = 10 marks
9.
A headload worker lifts a 40 kg sack of rice from the ground on to a lorry 1.5 m high in 4 s. (g = 10 m/s2) (a) Find the work he does against gravity. (b) Find his power.
(2)10.
A ball of mass 2 kg moves with a velocity of 3 m/s. (a) Find its kinetic energy. (b) What will its kinetic energy be if its velocity is doubled?
(2)11.
A girl pulls a box to the right along a table (figure). The forces on the box are: her pull, friction, the force of gravity and the upward force of the table. Which of these forces does (a) positive work, (b) negative work, (c) no work? Give a reason for (c).
(2)12.
A packet of biscuits gives 150 kcal of energy. (1 kcal = 4200 J) (a) Express this energy in joule. (b) If all of it could be used to climb, how high could a student of mass 50 kg rise? (g = 10 m/s2)
(2)13.
Water stored in the Idukki reservoir is used to light bulbs in our homes. Write the energy changes, in order, from the water in the dam to the light from a bulb.
(2)SECTION CAnswer all · 4 × 3 = 12 marks
14.
A stone of mass 2 kg is dropped from a height of 20 m (figure). Ignore air resistance; g = 10 m/s2. (a) Find its potential energy and kinetic energy at the top. (b) Find its potential energy and kinetic energy when it is 5 m above the ground. (c) Find its speed just before it hits the ground.
(3)15.
A motor pump lifts 600 kg of water into an overhead tank 10 m high in 2 minutes. (g = 10 m/s2) (a) Find the work done. (b) Find the power of the motor in watt. (c) Express it in horsepower.
(3)16.
Anu (mass 40 kg) runs up a staircase 6 m high in 12 s. Binu (mass 50 kg) climbs the same staircase in 20 s. (g = 10 m/s2) (a) Find the work done by each. (b) Find the power of each. (c) Who did more work? Who is more powerful?
(3)17.
A car of mass 1000 kg is moving at 72 km/h. (a) Express its speed in m/s. (b) Find its kinetic energy. (c) When the brakes are applied it stops after 40 m. Find the average braking force. Into which form does the kinetic energy change?
(3)SECTION DAnswer all · 2 × 5 = 10 marks
18.
The hammer of a pile driver has a mass of 500 kg. It is raised to a height of 5 m above the top of a pile and released (figure). Take g = 10 m/s2 and ignore air resistance. (a) How much work is done in raising the hammer? In which form is it stored? (b) What are the kinetic energy and the potential energy of the hammer just before it hits the pile (take the top of the pile as the zero level)? (c) Find its speed just before it hits the pile. (d) State the law that explains (b). (e) Assume all this kinetic energy is used to push the pile 0.25 m into the ground. Find the average resisting force of the soil.
(5)19.
A ball of mass 0.2 kg is thrown vertically upwards with a velocity of 20 m/s. Ignore air resistance; g = 10 m/s2. (a) Find its kinetic energy when it is thrown. (b) Find the maximum height it reaches. (c) Find its potential energy and kinetic energy at a height of 15 m. (d) Which graph in the figure shows how its kinetic energy changes with height? (e) Find the work done by gravity on the ball while it rises. Is it positive or negative?
(5)