Question

I have some doubts in the following questions:
Chapter : WORK , ENERGY AND POWER

1. A body of mass 2 kg is dropped from the top of a tower of height 100 m. If the acceleration due to gravity is 10 m/s2 calculate the K.E at the end of 5 seconds.

2. A body of mass 2 kg is thrown vertically upwards with an initial velocity of 20 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. What happens to its K.E as velocity becomes zero. Find the energy present in an object of mass 10 kg when it is at a height of 6m above the ground. Given g= 9.8 m/s2 .

4. A porter lifts a luggage of 15 kg from the ground and puts it on her head 2m above the ground. Calculate the work done by her on the luggage. (Take g= 10 m/s2 ).

5. A rocket of mass 3x 10 6 kg mass takes off from a launching pad and attains a 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. What is the P.E. if the object is allowed to fall, find the K.E when it is half way down. 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 3v respectively. Find the ratio of their kinetic energies.

9. What is the work done to increase the velocity of a car from 30 km/h to 60 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 of 36 km/h to 18 km/h. Find the work done by the brakes, assuming the mass of the empty scooter to be 86 kg and that of the person and petrol equal to 64 kg.

11. How much time will a pump of 1 kW power take to lift 500kg of water to height of 40 m ? (Take g=10m/s2 )

12. A horse exerts a pull on the cart of 300 N so that the horse-cart system moves with a uniform speed of 18 km/h on a level ground. Calculate the power developed by the horse in watt and also find its equivalent in horsepower. ​

Answer 1

Answer:

and energy are closely tied to the concept of force because an applied force can do work on an object and cause a change in energy. Energy is defined as the ability to do work.

Answer 2

Answer:

and energy are closely tied to the concept of force because an applied force can do work on an object and cause a change in energy. Energy is defined as the ability to do work

Explanation: