Advertisements
Advertisements
प्रश्न
In which one of the following cases is the work done more? When the angle between the direction of motion and that of the force is (i) 90° (ii) 0°.
Advertisements
उत्तर
When the angle between the direction of motion and that of the force is 90°;
W = Fd cos 90° = 0
When the angle between the direction of motion and that of the force is 0°;
W = Fd cos 0° = Fd
Hence in the second case, when the angle is 0°; the work done is more.
APPEARS IN
संबंधित प्रश्न
One horse power is equal to ______.
What do you mean by equilibrium of a body?
Work is a scalar quantity because it is a measure of transfer of energy without indicating any direction
A pump is used to lift 600 kg of water from a depth of 75 m in 10s. Calculate:
- The work done by the pump,
- the power at which the pump works, and
- The power rating of the pump if its efficiency is 40%. (Take g = 10m s-2).
`["Hint" : "Efficiency" = "useful power"/"power input"]`
It takes 20 s for a person A of mass 50 kg to climb up the stairs, while another person B of same mass does the same in 15 s. Compare the power developed by the persons A and B.
Give the units of couple.
State the condition when the work done by the force is negative.
State the S.I. and C.G.S. units of energy. How are they related?
The world record for weight lifting was held by Sergei Didyk of the USSR. He lifted 261 kg to a height of 2.3 m in 4s; find:
(a) Weight lifted by him
(b) Work done by him
(c) Power developed by him. (g = 10m/s2)
A force of 1 kgf displaces a body by a distance of 10 cm
(i) in direction of force,
(ii) normal to the force
(iii) at an angle of 60° to the direction of the force.
Calculate the amount of work done in each case. (Take: g = 9.8 ms−2 )
