Advertisements
Advertisements
प्रश्न
Why is a jack screw provided with a long arm?
उत्तर
A jack screw is provided with a long arm in order to have the effortless than the load. According to the principle of moments, load x load arm = effort x effort arm. So, if the load arm is more, then the effort will be more than the load.
APPEARS IN
संबंधित प्रश्न
Define 1 J of work.
In which of the following cases, is work being done?
(i) A man pushing a wall.
(ii) a coolie standing with a load of 12 kgf on his head.
(iii) A boy climbing up a staircase.
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 box of weight 150 kgf has gravitational potential energy stored in it equal to 14700 J. Find the height of the box above the ground. (Take g = 9.8 N kg-1)
Name the physical quantity whose SI unit is Nm.
What is the work done against gravity when a body is moved horizontally along a frictionless surface?
Give two examples of work done.
Distinguish between work and power.
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.
Define the term work. Name the CGS and SI unit of work.
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 girl of mass 40 kg runs a height of 80 stairs, each 25 cm high with a load of 20 kg on her head in 25 sec. If g is 10 m/s2, find:
(i) Gravitational force acting on the girl.
(ii) Work done by her.
(iii) Useful work done by her.
(iv) Her power in watt.
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.
