Advertisements
Advertisements
Question
An electric motor drives a machine which lifts a mass of 4 kg through a height of 10 m in 5 s at a constant speed. Assuming g = 10 ms-2, calculate
(i) the amount of work done, (ii) the power of the machine.
Solution
Given mass m = 4 kg,height h = 10m, time t = 5s
(i) work done = mgh = 4 x 10 x 10 = 400 j
(ii) power = `"work done"/"time taken" = 400/5` = 80 w
APPEARS IN
RELATED QUESTIONS
Power spent by a body depends on the time for which it does work.
A body of mass 5 kg falls from a height of 10 m to 4 m. Calculate:
The loss in potential energy of the body,
State two disadvantages of producing hydroelectricity.
Is work a scalar or a vector quantity?
Explain by an example that a body may possess energy even when it is not in motion.
Define the term 'work'. Write the formula for the work done on a body when a force acts on the body in the direction of its displacement. Give the meaning of each symbol which occurs in the formula.
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.
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°?
Draw a neat labeled diagram to show the direction of two forces acting on a body to produce rotation in it. Also mark the point about which rotation takes place.
A boy does work when he pushes against a brick wall. (yes/no).
Give two examples of work done.
Fill in the boxe to show the corresponding energy transformation.
State the energy changes which take place when Water stored in the dam is used to turn turbine in dynamo.
Give an example
Chemical energy changes to electrical energy.
A bucketful of water is to be drawn from a well ______ will be done when a ______ is applied to do this because there will be a ______ of water.
(displacement, work, force)
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.
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
Food grains are getting dried in the sun.
A man squatting on the ground gets straight up and stand. The force of reaction of ground on the man during the process is ______.
