Advertisements
Advertisements
प्रश्न
A car is running at a speed of 15 km h-1 while another similar car is moving at a speed of 45 km h-1. Find the ratio of their kinetic energies.
Advertisements
उत्तर
Given, velocity of first car, v1 = 15 km/h
And velocity of second car, v2 = 45 km/h
Since masses are same, kinetic energy is directly proportional to the square of the velocity (Kav2)
Hence, ratio of their kinetic energies is:
`therefore k_1/k_2 = v_1^2/v_2^2`
`therefore k_1/k_2 =15^2/45^2`
`therefore k_1/k_2 = (cancel(15)^1 xx cancel(15)^1)/(cancel(45)_3 xx cancel(45)_3)`
`therefore k_1/k_2 = 1/(3 xx 3)`
`therefore k_1/k_2 = 1/9`
∴ k1 / k2 = 1 : 9
APPEARS IN
संबंधित प्रश्न
An electron emitter must have _____________ work function and ___________ melting point.
In which of the following cases, is work being done?
(i) A man pushing a wall.
(ii) a coolie standing with a load of 12 kgf on his head.
(iii) A boy climbing up a staircase.
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)
A vessel containing 50 kg of water is placed at a height 15 m above the ground. Assuming the gravitational potential energy at ground to be zero, what will be the gravitational potential energy of water in the vessel? (g = 10 m s-2)
A boy throws a rubber ball vertically upwards. What type of work, positive or negative, is done : by the force applied by the boy?
(a) by the force applied by the boy?
(b) by the gravitational force of earth?
Explain by an example that a body may possess energy even when it is not in motion.
Can every force produce work?
A block of mass 20 kg is pulled up a slope (fig.12) with a constant speed by applying a force of 500 N parallel to the slope. A and B are initial and final positions of the block.
(a) Calculate the work done by the force in moving the block from A and B.
(b) Calculate the potential energy gained by the block.
Look at the activity below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
A donkey is carrying a load on its back.
