Comprehension Questions | Physics 9th | Chapter 6 Work & Energy | National Book Foundation Islamabad
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Under what condition, work done
Under what condition, work done on the body is maximum and minimum?
Why is only horizontal component of the force acting on the body involved in expression of work?
If a bucket of water having mass of 20kg is carried by a person through distance of 10m, calculate the work done by the person in carrying the bucket.
Give an example of negative work done by a body?
Describe the situation in which no work is done, although force is acting on the body and it is covering some displacement.
A car has kinetic energy ‘K’. What will be effect on its kinetic energy if its velocity is doubled?
Why is potential energy stored in the body when it is lifted to some height from surface of earth?
Work done on the body either speed it up or slows it down or raises it up. Keeping it in mind, tell how much work is done by centripetal force on the orbiting satellite?
A bullet is fired from gun, bullet penetrates into a sand wall and it stops. Where is its kinetic energy used?
An energy saver bulb has efficiency of 80%. What does it mean?
Tides can be used to generate electrical energy. Discuss a method to convert tidal energy into electrical energy?
Define work. Derive its expression. Also define its unit. Discuss different cases of work.
What is mechanical energy? What are its different types?
Define kinetic energy of a body. Derive its expression.
Define potential energy? What are its different types? Define gravitational potential energy. Derive its expression.
Define the terms: input, output and efficiency. Discuss the meaning of efficiency of a machine is your own words.
Explain the meaning of conservation of energy using different examples.
Define power. What is formula? Define its SI unit. What is its relation with power?
What do you mean by non-renewable energy sources and renewable energy sources? Discuss some renewable and non-renewable energy sources.
Describe the process of electricity generation by drawing a block diagram of the process from fossil fuel input to electricity output.
Explain by drawing energy flow diagrams through steady state systems such as Filament lamp, a power station, a vehicle traveling at a constant speed on a level road.
Calculate the work done in pushing a box with 150N through distance of 5m?
A little boy is pulling his toy trolley by applying force of 20N at angle of 60° with ground and trolley moves through 5m. What is the work done by the boy.
In which case more work is done
a. A block of 100N is lifted straight up to height of 4m.
b. 50N force is required to move the same block to same height with the help inclined plane of length 5m.
A mason of 600N weight is climbing on a 12m high ladder. Find his P.E at the middle of ladder.
A boy weighing 75N jumps up and gains 300J of P.E. What height did the boy reach?
A 5kg steel ball is at the top of a tower of height 12m. It is dropped. What is kinetic energy of the ball on hitting the ground? With what velocity, it will hit the ground? (Neglect the air resistance)
A 2hp electric motor gives energy to a pulley system that lifts a load of 10kg to height of 10m in 1.5s. Calculate
a. Input (work done by motor on pulley system) b. Output (load lifted)
c. Efficiency of pulley system
A man weighing 60kg climbs upstairs with 20kg weight on his head. The stair case has 20 steps, each being 15cm high. If he takes 10 seconds to climb, find his power in watts and in horse power?
Why is only horizontal component of the force acting on the body involved in expression of work?
If a bucket of water having mass of 20kg is carried by a person through distance of 10m, calculate the work done by the person in carrying the bucket.
Give an example of negative work done by a body?
Describe the situation in which no work is done, although force is acting on the body and it is covering some displacement.
A car has kinetic energy ‘K’. What will be effect on its kinetic energy if its velocity is doubled?
Why is potential energy stored in the body when it is lifted to some height from surface of earth?
Work done on the body either speed it up or slows it down or raises it up. Keeping it in mind, tell how much work is done by centripetal force on the orbiting satellite?
A bullet is fired from gun, bullet penetrates into a sand wall and it stops. Where is its kinetic energy used?
An energy saver bulb has efficiency of 80%. What does it mean?
Tides can be used to generate electrical energy. Discuss a method to convert tidal energy into electrical energy?
Define work. Derive its expression. Also define its unit. Discuss different cases of work.
What is mechanical energy? What are its different types?
Define kinetic energy of a body. Derive its expression.
Define potential energy? What are its different types? Define gravitational potential energy. Derive its expression.
Define the terms: input, output and efficiency. Discuss the meaning of efficiency of a machine is your own words.
Explain the meaning of conservation of energy using different examples.
Define power. What is formula? Define its SI unit. What is its relation with power?
What do you mean by non-renewable energy sources and renewable energy sources? Discuss some renewable and non-renewable energy sources.
Describe the process of electricity generation by drawing a block diagram of the process from fossil fuel input to electricity output.
Explain by drawing energy flow diagrams through steady state systems such as Filament lamp, a power station, a vehicle traveling at a constant speed on a level road.
Calculate the work done in pushing a box with 150N through distance of 5m?
A little boy is pulling his toy trolley by applying force of 20N at angle of 60° with ground and trolley moves through 5m. What is the work done by the boy.
In which case more work is done
a. A block of 100N is lifted straight up to height of 4m.
b. 50N force is required to move the same block to same height with the help inclined plane of length 5m.
A mason of 600N weight is climbing on a 12m high ladder. Find his P.E at the middle of ladder.
A boy weighing 75N jumps up and gains 300J of P.E. What height did the boy reach?
A 5kg steel ball is at the top of a tower of height 12m. It is dropped. What is kinetic energy of the ball on hitting the ground? With what velocity, it will hit the ground? (Neglect the air resistance)
A 2hp electric motor gives energy to a pulley system that lifts a load of 10kg to height of 10m in 1.5s. Calculate
a. Input (work done by motor on pulley system) b. Output (load lifted)
c. Efficiency of pulley system
A man weighing 60kg climbs upstairs with 20kg weight on his head. The stair case has 20 steps, each being 15cm high. If he takes 10 seconds to climb, find his power in watts and in horse power?
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