Advertisements
Advertisements
Question
Complete the following sentences:
The SI unit of work is ....... and of power is .......
Solution
The SI unit of work is joule and of power is watt
APPEARS IN
RELATED QUESTIONS
Power spent by a body depends on the time for which it does work.
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.
A boy weighing 25 kgf climbs up from the first floor at height 3 m above the ground to the third floor at height 9m above the ground. What will be the increase in his gravitational potential energy? (Take g = 10 N kg -1)
What do you mean by degradation of energy?
Fill in the blank with suitable word :
1 joule is the work done when a force of 1 __________ moves an object through a distance of one __________ in the direction of __________.
Is it possible that a force is acting on a body but still the work done is zero? Explain giving one example.
A person of mass 50 kg climbs a tower of height 72 metres. Calculate the work done. (g = 9.8 m s−2).
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?
A boy tries to push a truck parked on the roadside. The truck does not move at all. Another boy pushes a bicycle. The bicycle moves through a certain distance. In which case was the work done more : on the trick or on the bicycle? Give a reason to support your answer.
Draw a neat labeled diagram to show the direction of two forces acting on a body to produce rotation in it. Also mark the point about which rotation takes place.
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.
State the energy changes which take place when Water stored in the dam is used to turn turbine in dynamo.
Give an example
Electrical energy changes of sound energy.
A truck driver can load oil drums into the back of the truck by pushing them up a sloping plank, or by lifting them directly. Each drum has a mass of 80 kg, the plank is 3 m long, and the back of the truck is 0.8 m above the ground.
(i) How much force would be needed to lift a drum into the truck directly/without using the plank? (Take g = 10 m/s2)
(ii) How much energy would be required in lifting the drum into the truck without the plank?
(iii) If the force needed to push the drum up the plank is 300 N, why is this less than the answer to part (i)?
(iv) When the truck is loaded, the driver drives off. List the major energy changes that take place in moving the truck.
(v) The driver has to stop at the factory gates. What happens to the kinetic energy of the truck?
The weights of two bodies are 2.0 N and 2.0 kgf respectively what is the mass of each body?
An electric motor pump is 60% efficient and is rated 2.5 H.P. Calculate the maximum load it can lift through a height of 10m in 8 sec. (1 H.P. = 750 W).
________ is said to be done when a force is acting on it.
State whether work is done or not, by writing yes or no, in the following case:
A man pushes a wall.
