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Questions
State the S.I. unit of energy.
Solution
S.I. unit of energy Joule (J).
RELATED QUESTIONS
Why is a jack screw provided with a long arm?
Name a common device where a gear train is used
A coolie is moving on a road with a luggage on his head. Does he perform work against the force of gravity? Give reason for your answer.
MULTIPLE CHOICE TYPE
In an electric cell which in use, the change in energy is from:
A boy weighing 25 kgf climbs up from the first floor at height 3 m above the ground to the third floor at height 9m above the ground. What will be the increase in his gravitational potential energy? (Take g = 10 N kg -1)
A bullet of mass 0.5 kg slows down from a speed of 5 m s-1 to that of 3 m s-1. Calculate the change in kinetic energy of the ball.
Fill in the blank with suitable word :
Work is measured as a product of __________ and __________
When do we say that work is done? Write the formula for the work done by a body in moving up against gravity. Give the meaning of each symbol which occurs in it.
In which of the following case the work done by a force will be maximum : when the angle between the direction of force and direction of motion is 0° or 90°?
A girl weighing 400 N climbs a vertical ladder. If the value of g be 10 m s−2, the work by her after climbing 2 m will be :
Name five appliances or machines which use an electric motor.
Why is the work done on an object moving with uniform circular motion zero?
Give two examples of couple action in our daily life.
P, Q and R are three forces which act as shown in fig.
The point O lies in the same plane. Given, P = Q = R = 10N
(i) Which force has the least moment about O? Give a reason.
(ii)Which force has the greatest moment about O? Give a reason.
A uniform circular motion is an accelerated motion. Justify it.
Is the motion of moon around the earth in circular path an accelerated motion?
What is the SI unit of work?
Nm is the unit of .......
A man lifts a mass of 10 kg from the floor to a shelf 4 meter high. If g = 10 ms-2, what is the work done?
What is the ratio of SI units to CGS units of 'work'?
Distinguish between work and power.
Complete the following sentences:
Joule is the unit of .......
A machine raises a load of 750 N through a height of 16 m in 5s. calculate:
(i) work done by machine,
(ii) power at which the machine works.
State the energy changes which take place when Water stored in the dam is used to turn turbine in dynamo.
State the energy changes which take place when An electric bulb glows when it is connected to a source of electric current.
How much energy is gained by a box of mass 20 kg when a man, runs carrying the box with a speed of 3 m/s-1 to catch the bus?
A coolie, with a load of 30 kg on his head, walks on the platform. If he walks a distance of 60 m, what is the work done by him?
State larger units of power.
A man climbs a slope and another walks same distance on level road. Which of the two expends more energy and why?
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A green plant is carrying out photosynthesis.
A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments; one in which the charged particle is also a proton and in another, a positron. In the same time t, the work done on the two moving charged particles is ______.
Work done by this force at any instant is ______.
