Question

016. A force acting on a 20 kg mass changes its velocity from 5m/s to 2 m/s. Calculate the work
done.
QIZ The K.E. of an object of mass m moving with a velocity of 5m/s is 25 J. What will be its KE.
when its velocity is doubled? What will be its K.E when its velocity is increased 3 times?
Q18. An object of mass 12 kg is at a certain height above the ground. If the gravitational P. E. is 480
find the height at which the object is w.r.t the ground (g=10m/s 2)​

Answer 1

Answer:

Explanation:A force acting on a 20 kg mass changes its velocity from 5m/s to 2 m/s. Calculate the work

ans: Work done by a given force = change in kinetic energy

       Work done by the force = ½×m(v²-u²)

        Work done by the force = ½×20(2²-5²)

        Work done by the force = 10(4-25)

        Work done by the force = 10(-21)

       Work done by the force = - 210 Joules

An object of mass 12 kg is at a certain height above the ground. If the gravitational P. E. is 480

find the height at which the object is w.r.t the ground (g=10m/s 2)​

ans:

Potential energy = mgh

Where,

m = Mass

g = Acceleration due to gravity

h = Height

ACCORDING THE QUESTION,

➟ 12 × 10 × h = 480

➟ 120 × h = 480

➟ h = 480 / 120

➟ h = 48 / 12

➟ h = 4

The height of the object is 4m.

More Information

Some more important concepts related to energy :-

Potential energy = m × g × h

Kinetic energy = 1/2 × m × v²

The S.I. unit of energy is Joule ( J ).

Potential energy = Work done

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