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संबंधित प्रश्न
Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?
A boy of mass 40 kg climbs up the stairs and reaches the roof at a height 8 m in 5 s. Calculate:
- the force of gravity acting on the boy,
- the work done by him against the force of gravity,
- the power spent by boy. (Take g = 10 m s-2)
A vessel containing 50 kg of water is placed at a height 15 m above the ground. Assuming the gravitational potential energy at ground to be zero, what will be the gravitational potential energy of water in the vessel? (g = 10 m s-2)
Give one example each in which a force does (a) positive work (b) negative work, and (c) zero work.
What is the ratio of SI units to CGS units of 'work'?
Write an expression for the work done against gravity.
Is power a scalar quantity?
A boy pulls a box up to 10 m with a force of 5 kgf. Calculate the work done by him.
A girl of mass 50 kg runs up a flight of 40 steps in 20 seconds. If each step in 20 cm high, calculate the power developed by the girl. (g= 10 ms-2).
State the energy changes which take place when An electric bulb glows when it is connected to a source of electric current.
Give an example
Chemical energy changes to heat energy.
Give an example
Electrical energy changes to heat energy.
How is horse power related to the S. I. unit of power?
Define Translational motion.
(i) A 200g ball is thrown vertically upward with an initial velocity of 30 ms-1. Draw a velocity-time graph for the motion of ball.
(ii) How long will the ball take to reach the highest point?
(iii) What will be the kinetic energy of ball, when it returns to the starting point, neglecting the air resistance?
(iv) What will be the potential energy of ball at highest point?
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
Suma is swimming in a pond.
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A donkey is carrying a load on its back.
A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity. In this process the potential energy of the car
