Advertisements
Advertisements
प्रश्न
A man squatting on the ground gets straight up and stand. The force of reaction of ground on the man during the process is ______.
विकल्प
constant and equal to mg in magnitude.
constant and greater than mg in magnitude.
variable but always greater than mg.
at first greater than mg, and later becomes equal to mg.
Advertisements
उत्तर
A man squatting on the ground gets straight up and stand. The force of reaction of ground on the man during the process is at first greater than mg, and later becomes equal to mg.
Explanation:
When the man is squatting on the ground he is tilted somewhat, hence he also has to balance frictional force besides his weight in this case.
R = reactional force = friction + mg
⇒ R > mg
When the man gets straight up in that case friction ≈ 0
⇒ Reactional force ≈ mg
APPEARS IN
संबंधित प्रश्न
Write an expression for the work done when a force is acting on an object in the direction of its displacement.
Explain briefly why the work done by a fielder when he takes a catch in a cricket match is negative.
An electron emitter must have _____________ work function and ___________ melting point.
No work is done by a force if the body
In which of the following cases is work being done:
- A boy pushing a heavy rock
- A boy climbing up the stairs
- A coolie standing with a box on his head
- A girl moving on the road.
Give reasons for the following A teacher moving around in the class is doing work but a child standing and reading a book is not doing any work.
Express joule in terms of erg.
MULTIPLE CHOICE TYPE
In an electric cell which in use, the change in energy is from:
Nm is the unit of .......
What do you mean by a kilo joule?
Define 'joule'.
On what factors does the work done by a force depend?
Write an expression for work done by a force depends?
A weight lifted a load of 200 kgf to a height of 2.5 m in 5 s. calculate: (i) the work done, and (ii) the power developed by him. Take g= 10 N kg-1.
(a) Define power and name its unit.
(b) A girl weighting 50 kg climbs up 60 steps each of 20 cm height in 5 minutes. Calculate the power developed.
A proton is kept at rest. A positively charged particle is released from rest at a distance d in its field. Consider two experiments; one in which the charged particle is also a proton and in another, a positron. In the same time t, the work done on the two moving charged particles is ______.
State whether work is done or not, by writing yes or no, in the following case:
A boy climbs up 20 stairs.
