Advertisements
Advertisements
Question
A satellite revolves around the earth in a circular orbit. What is the work done by the force of gravity? Give reason.
Solution
The centripetal force, which generates the force of gravity, does no work. The satellites have accomplished nothing at all. This is due to the fact that the Earth is the satellite's centre of mass and that the displacement is always along the tangent to the circular route, or normal to the direction of force on the satellite. (θ = 90°)
Displacement of satellite is normal to the direction of force
where, O - Earth, S - Displacement, F - Force of gravity
W = F × S cos 90°
W = F × S × 0 = 0
APPEARS IN
RELATED QUESTIONS
A boy weighing 40 kgf climbs up a stair of 30 steps each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes. Compare:
- The work done by them.
- The power developed by them.
A stone of mass m is rotated in a circular path with a uniform speed by tying a strong string with the help of your hand. Answer the following questions
1) Is the stone moving with a uniform or variable speed?
2) Is the stone moving with a uniform acceleration? In which direction does the acceleration act?
3) What kind of force acts on the hand and state its direction?
Draw a simplified diagram of a lemon crusher, indicting of load and effort
One horse power is equal to ______.
The moment of a force 10 N about a point 0 is 4 Nm. Calculate the distance of point of application of force from the point 0.
State two conditions for work to be done.
Justify the statement. “Power can be expressed as the product of force and velocity.”
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 boy weighing 50 kgf climbs up from the first floor at a height of 3 m above the ground to the third floor at a height of 9 m above the ground. What will be the increase in his gravitational potential energy? (Take g = 10 N kg-1).
