class 9 kinetic engergy practice sheet

 

                                            Class 9

                                 Practice Sheet-1  (Kinetic Energy and Potential Energy)

Q 1      MULTIPLE CHOICE QUESTIONS

(1) When the speed of a moving body is doubled, its

a)      a) Acceleration is doubled   b) weight is doubled c) kinetic energy is double d) kinetic energy increases by 4 times.

(2). Two masses of 1g and 4g are moving with equal kinetic energies .The ratio of the magnitudes of their linear momenta is

a)     a)  4:1          b) 5:0.6             c) 1:2                          d) 1:16

(3).Kinetic energy of the body is proportional to

      a) Velocity     b) Its weight     c) its momentum     d) square of its velocity.

(4) If the momentum of a body increases by 50%, then its kinetic energy increases by

a)      a) 25%       b) 50%               c) 100%                     d) 125%

(5)A body at rest may possess

a) K.E           b) P.E                 c) momentum          d) none of these

(6)Water stored in a dam possess

a) No Energy     b) Electrical Energy    c) Kinetic Energy    d) Potential Energy

(7) Which of the following, is not an example of potential energy?

(a) Water stored in a dam. (b) A Stretched bow, and an arrow system. (c) A Dog chasing a hare.

Q2 STATE TRUE OR FALSE FOR THE FOLLOWING:

a)       A moving truck has more kinetic energy than a bicycle moving with the same speed.

b)      Kinetic Energy is a vector quantity.

c)       In an oscillating pendulum the kinetic energy is maximum at extreme position.

d)      Falling of water from the dam has kinetic energy.

e)      A Bag, lying, on a table, possess only kinetic energy.

Q3 SHORT ANSWER QUESTIONS:

a)       Two objects have different masses but the same kinetic energy. If you stop them with the same retarding force, which one will stop in the shorter distance?

b)      What type of energy is possessed by a cricket ball just before being caught by a fielder?

c)       A body is thrown up, its velocity goes on decreasing .What happens to its kinetic energy as its velocity becomes zero?

d)      How does the wind move the blades of a wind-mill?

e)      How is energy stored in a clock?

f)        What happens to the potential energy, of a slinky, when it is stretched and compressed?

g)       What type of energy, a man possess, while standing at the top of a building?

h)      How is the potential energy affected, when work done, by a body? And, when work done on a body?

Q4.  a) ASSERTION: The Kinetic Energy,with any reference must be  positive .

           REASON: In the Expression for kinetic energy, the velocity appears with power 2 and mass is a

                scalar quantity.

b)      ASSERTION: The change in Kinetic energy of a particle is equal to work done on it by the net force.

REASON: Change in kinetic energy of a particle is equal to the work done only in case of system of one particle.

c)       ASSERTION: A winded  toy car, when placed on the floor, starts moving

REASON:  Toy car has kinetic energy stored in it which makes its motion.

d)      ASSERTION: A light body and heavy body have same momentum. Then they also have same kinetic energy.

REASON: Kinetic energy depends on the mass of the body.

e)      ASSERTION: Graph, between, the potential energy of spring vs. the extension or compression of a string is a straight line.

REASON: Potential Energy of a stretched or compressed string is directly proportional to square of extension or compression.

Q5. Solve the following numerical:

a)       A horse and a Dog are running with the same speed. What is the ratio of their kinetic energy if the mass of the horse is 10 times that of dog?

b)      A bullet  of mass 5g travels with  a speed of 500m/s .If it penetrates a fixed target which offers a constant resistive force of 1000N to the motion of the bullet, find

(1)    The initial K.E of the bullet

(2)    The distance through which the bullet has penetrated.

c)       The car of mass 1200kg is moving with a speed of 80km/hr. Calculate the kinetic energy of the car.

d)      A body of mass 5kg initially at rest is subjected to a force of 20 N. What is the Kinetic Energy acquired by the body at the end of 10sec.?

e)      A man drops a 10kg rock from the top of a 5m ladder. What is its kinetic energy when it reaches ground? What is its speed before it hits the ground?

f)        An object of mass 1kg is raised through a height ‘h’.  Its Potential energy is increased by 1J. Find the height h.

g)       A man of 50kg, jumps from height of 1.2m. What is the potential energy, at the highest point?

h)      A skier of mass 50kg stands at A, at the top of a ski jump. He takes off at A for his jump to B. Calculate the potential energy between A and B.