Advertisements
Advertisements
प्रश्न
How fast should a boy weighting 30 kg run so that his kinetic energy is 375 joule?
उत्तर
We know that , K.E = `1/2` mv2
375 = `1/2` x 30 x v2
or v2 = `(375 xx 2)/30` = 25 m/s
or v = 5 m/s
APPEARS IN
संबंधित प्रश्न
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)
The work done by a force acting obliquely is given by the formula : W = F cos θ ✕ s. What will happen to the work done if angle θ between the direction of force and motion of the body is increased gradually? Will it increase, decrease or remain constant.
A boy tries to push a truck parked on the roadside. The truck does not move at all. Another boy pushes a bicycle. The bicycle moves through a certain distance. In which case was the work done more : on the trick or on the bicycle? Give a reason to support your answer.
Name the physical quantity whose SI unit is Nm.
A man carrying a suitcase in his hand is walking horizontally. What is the work done against gravity?
Write an expression for the work done against gravity.
State the amount of work done by an object when it moves in a circular path for one complete rotation. Give a reason to justify your answer.
Calculate the work done when:
A 5 kg weight is lifted 10 m vertically. (g = 9.8 m/s2)
The weights of two bodies are 2.0 N and 2.0 kgf respectively what is the mass of each body?
If a ball is dropped on the sloping roof of a house, it acquires ______ and falls on the ground. That is the transformation of ______ energy into ______ energy takes place.
(kinetic, potential, motion)
Write the two main conditions are needed for work to be done?
What is work?
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 wind-mill is lifting water from a well.
