# I have some doubts in the following questions:Chapter : WORK , ENERGY AND POWER1. A body of mass 2 kg is dropped from the top of a tower of height 100 m. Ifthe acceleration due to gravity is 10 m/s2calculate the K.E at the end of 5seconds.2. A body of mass 2 kg is thrown vertically upwards with an initial velocity of20 m/s2. What will be its P.E at the end of 2 s . ( Take g as 10 m/s2)3. A body is thrown vertically upwards .its velocity keeps decreasing. Whathappens to its K.E as velocity becomes zero. Find the energy present in anobject of mass 10 kg when it is at a height of 6m above the ground. Giveng= 9.8 m/s2.4. A porter lifts a luggage of 15 kg from the ground and puts it on her head 2mabove the ground. Calculate the work done by her on the luggage. (Take g=10 m/s2).5. A rocket of mass 3x 10 6kg mass takes off from a launching pad and attainsa velocity of 1 km/h at an attitude of 25 km. Calculate the P.E and K.E .(Take g=10m/s2)6. An object of mass 40 kg is raised to a height of 5m above the ground. Whatis the P.E. if the object is allowed to fall, find the K.E when it is half waydown. Take g as 10 m/s2.7. A boy of mass 40 kg runs up a flight of 15 steps, each 15 cm high in 10 s.Find the work done and the power developed by him. (Take g=10m/s2)8. Two bodies of equal masses move with uniform velocities of v and 3vrespectively. Find the ratio of their kinetic energies.9. What is the work done to increase the velocity of a car from 30 km/h to60 km/h. Let the mass of the car be 1500 kg.10. On a level road, a scooterist applies brakes to slow down from a speed of36 km/h to 18 km/h. Find the work done by the brakes, assuming the massof the empty scooter to be 86 kg and that of the person and petrol equal to64 kg.11. How much time will a pump of 1 kW power take to lift 500kg of water toheight of 40 m ? (Take g=10m/s2)12. A horse exerts a pull on the cart of 300 N so that the horse-cart systemmoves with a uniform speed of 18 km/h on a level ground. Calculate thepower developed by the horse in watt and also find its equivalent inhorsepower.

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