Advertisements
Advertisements
Question
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.
Advertisements
Solution
W = FS cos θ
Where,
(F) - Force
(W) - Work
(S) - Displacement
θ - Angle between F and S
When F and S are parallel, θ = 0.
Then, work done is, W = FS
RELATED QUESTIONS
When do we say that work is done?
Explain briefly why the work done by a fielder when he takes a catch in a cricket match is negative.
What is the work done by the moon when it revolves around the earth?
A force acts on a body and displaces it by a distance S in a direction at an angle θ with the direction of the force. What should be the value of θ to get the maximum positive work?
The moon is revolving around the earth in a circular path. How much work is done by the moon?
A boy of weight 40 kgf climbs up the 15 steps, each 15 cm high in 10 s and a girl of weight 20 kgf does the same in 5 s. Compare:
- the work done, and
- the power developed by them. Take g = 10 N kg-1.
MULTIPLE CHOICE TYPE
In an electric cell which in use, the change in energy is from:
Fill in the blank with suitable word :
The work done on a body moving in a circular path is __________
A boy throws a rubber ball vertically upwards. What type of work, positive or negative, is done : by the force applied by the boy?
(a) by the force applied by the boy?
(b) by the gravitational force of earth?
What should be the angle between the direction of force and the direction of motion of a body so that the work done is zero?
Choose one or more correct alternatives.
Joule is the unit of ______.
- force
- work
- power
- energy
Give two examples of couple actions in our daily life.
Nm is the unit of .......
Complete the following sentences:
Kilowatt is the unit of ....... and kWh is the unit of
Give an example
Chemical energy changes to heat energy.
Name the material commonly used for the manufacturing of solar cells.
A block of mass 30 kg is pulled up a slope, as shown in diagram with a constant speed, by applying a force of 200 N parallel to slope.
A and B are initial and final positions of block.
(i) Calculate the work done by force in moving the block from A to B.
(ii) Calculate P.E. gained by block. [g=10ms-2]
A water pump raises 50 kg of water through a height of 25 m in 5s. Calculate the power supplied by the pump (Take: g = 10 N kg−1).
