Physics full notes of class 11 ch4
Correct options with their questions numbers.
1 = B , 2 = C , 3 = C , 4 = A , 5 = B , 6 = C , 7 = C , 8 = B , 9 = C , 10 = A , 11 = A , 12 = D , 13 = D , 14 = B
Physics full notes of class 11 ch4 McQs end.
Question 1. A bucket is taken to the bottom of a well , does the bucket posses any potential energy (P.E) Explain ?
Answer: Yes, when a bucket is taken to the bottom of a well some work is to be done agianst the upthrust of water. This work is done is stored in the form of potential energy in the bucket. We can also that the bucket posses some negative potental energy with reference to the ground level.
Question 2. When an arrow is shot from its bow, it has kinetic energy (K.E) . From where does it get the K.E ?
Answer: To stretch the string of the bow, work is done on it. This work done is stored in the string as elastic potential energy.On releasing the string of the bow, the kinetic energy of the arrow and makes it move in the forward direction.
Thus the arrow gets its kinetic energy from the potental of the bow.
Question 3. Does a hydrogen filled balloon possess any potental energy ? explain ?
Answer: Yes, A hydrogen filled ballon possess potental energy. The hydrogen filled balloon is less denser than air, So when it is released in air, it moves in upward direction agianst gravitational field due to upthrust of air. Thus work is done by the upthrust of air on the balloon which is stored in the form of potental energy (P.E) in the balloon.
Question 4. Is kinetic energy (K.E) a vector quantity ?
Answer: We know that , K.E = 1/2 mv (square) —— 1.
In equation 1 ‘m’ represents the mass of a body which is a scalar quantity. While ‘V square’ represents the magnitude of velocity. As the magnitude represents a scalar quantity. So kinetic energy is a scalar quantity . The kinetic energy depends upon the magnitude of velocity . It does not depends upon the direction of velocity . Therefore kinetic energy is a scalar quantity.
Question 5 Answer: A target offers resistive force to a bullet , When it penetrates into it. The resistive force offered by the target does negative work on the bullet. So some of the kinetic energy is used against the resistive force of the material. Some part of kinetic energy may also be appear in the form of potental energy and heat energy also in the form of sound energy.
Question 6 Answer: We know that ,
W = F.D —–1
Where ‘F’ is applied force and ‘d’ is displacement covered. Since in case of of swinging pendulum , no displacement is covered along the string i-e in the direction of the tension in the string, so we put s = 0 in equation 1 , So we get ,
w = F.0 , w=0
Therfore the tension in the string of a swinging pendulum does not work as there is no displacement covered in the direction of the tension in the string.
Question 7 Answer: When a meteor enters into earths atmosphere it burns due to friction between air particles and its body. Hence the energy possessed by a meteor is converted into heat and light energy due to which the energy of the particles of the medium (air) increases.
Question 8 Answer: Elastic potental energy is stored in the spring of a watch , which is given by,
P.E = 1/2 kx (x square)
Question 9 Answer: When a man drops a cup
from a certain height, its potental energy is converted into kinetic energy when the cup strikes the ground , it breaks into pieces and its kinetic energy is converted into heat and sound energy.
Question 10 Answer: No work is done by the man rowing boat upstream, If he is at rest with respect to the shore. We know that w=F.d
As no displacement is covered by the boat , so we put d = 0 in equation so we get w=F.0, w=0. So no work is done by the man rowing a boat upstream. If he is at rest with respect to the shore.
Question 11 Answer: Energy savers are used instead of normal bulb due to the following reasons:
a. The consumption os energy in energy savers in far less than normal light bulbs.
b. Energy savers produces light of high power intensity as compared to normal light bulbs.
c. Energy savers are of long lives as compared to normal light bulbs.
d. Energy savers are more safer than ordinary light bulbs , as they produce very little amount of heat.
Physics full notes of class 11 ch4 short questions end.