Advertisements
Advertisements
Question
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
Solution
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
RELATED QUESTIONS
State two factors on which the work done on a body depends.
A boy of mass 40 kg climbs up the stairs and reaches the roof at a height 8 m in 5 s. Calculate:
- the force of gravity acting on the boy,
- the work done by him against the force of gravity,
- the power spent by boy. (Take g = 10 m s-2)
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)
State the law of conservation of energy.
Determine the amount of work done when an object is displaced at an angle of 30° with respect to the direction of the applied force.
How fast should a boy weighting 30 kg run so that his kinetic energy is 375 joule?
Fill in the boxe to show the corresponding energy transformation.
