Advertisements
Advertisements
प्रश्न
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.
Advertisements
उत्तर
(i) Gravitational force acting on the girl = Her mass in kg × g
= 40 × 10 = 400 N.
(ii) Total gravitational force = (Mass of girl + load) × g
= (40 + 20) × 10 = 600 N.
and Distance or height =`(80xx25)/100` = 20 m.
∴ Work done by her = 600 N × distance
∴ Total work done = 600 N × 20 m = 12000 J.
(iii) Useful work done = Load × g × Distance covered
= 20 × 10 × 20 = 4000 J.
(iv) Power = `("Total work done")/("Time")=12000/25"W"` = 480 W.
संबंधित प्रश्न
In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east, as shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero.
A man lifts a mass of 20 kg to a height of 2.5 m. Assuming that the force of gravity on 1 kg mass is 10 N, find the work done by the man.
.A man raises a box of mass 50kg to a height of 2m in 20s, while another man raises the same box to the same height in 50s. Compare:
(i) the work done, and
(ii) the power developed by them.
Explain degradation of energy by taking two examples of your daily life.
Explain by an example that a body may possess energy even when it is not in motion.
What is the relationship between Nm and dyne cm?
Give an example
Electrical energy changes of sound energy.
Calculate the work done when:
A 5 kg weight is lifted 10 m vertically. (g = 9.8 m/s2)
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 ______.
