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An important facility for 11th class students preparing for short questions physics 11th class chapter 4 of BISE. Get hundreds of questions to prepare and get better marks in 11th physics
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Question: 1
Write the term of Kinetic and Potential energy
Answer: 1
1-21
Kinetic Energy: We observe daily that, as moving object has the ability to push away another object at rest. Thus it is the capacity to do work because of its motion. Thus K.E. is defined as:
Velocity of boyd, then:
K.E.= 1/2 mv2
Potential Energy: In daily life we see that, if we lift a brick from ground to the top of a roof, work id done against the force of gravity. This appears as P.E. of brick, Thus P.E. IS defined as:
If m is mass, g is acceleration due to gravity and h is height of body form surface of earth , then
P.E. mgh
Question: 2
Define and explain the terms: Input, Output, efficiency for a machine.
Answer: 2
2-21
Question: 3
What do you understand by the term work? Explain
Answer: 3
3-21
Question: 4
Is any wrok done by centripetal force?
Answer: 4
4-21
Question: 5
A Bucket is taken to the bottom of a well does the bucket posses any P.E.?
Answer: 5
5-21
Yes the bucket will possess negative potential energy.
Explanation:
* Work is done by gravitational forfe
* Its potential energy is decreased because it mvoes down
* The potential energy on the surface is taken to be zero, thereforeis inside the well, potential energy will be negative.
Question: 6
Define Gravitational potential. Write its formula.
Answer: 6
6-21
Question: 7
Define commercial unit of electrical energy.
Answer: 7
7-21
Question: 8
Derive work energy relation of principle.
Answer: 8
8-21
Question: 9
Block and tackle system of pulleys is used ot raise a load of 500 N through a heigh tof 20 m. The work done against friction is 2000 J. Calculate the (a) work done by the effor (b) the efficiency of the system.
Answer: 9
9-21
Question: 10
is frictional force conservative force?Explain
Answer: 10
10-21
Question: 11
Give examples of variable force?
Answer: 11
11-21
Question: 12
When an arrow is shot from its bow it has. K.E. from where does it get the K.E.
Answer: 12
12-21
The arrow gets the K.E. from elastic potential eneryg of the bow.
Explanation:
When we stretch the rubber of the bow from its mean position.
* Work is done on it which is stored in rubber in the form of elastic energy.
* When arrow is released the elastic potential energy is gtransformed into kinetic energy.
Work done = P.E.
Loss in P.E.= Gain in K.E.
Question: 13
A meter when enters into the earth's atmosphere burns, what happens to its energy?
Answer: 13
13-21
When meteor enters the earth atmosphere then air friction acts on it. /the huge amount of energy is used against the resstive force of the atmosphere , in bringing the meteour to rest. The loos of K.E. appars in the form of heat energy which burns the meteor to asbes.
Question: 14
What type od energy is stored in he spring of watch?
Answer: 14
14-21
A compressed spring of watch stores eleastic P.E. in it. which is givne by formula.
P.E = 1/2 Kx2
This elastic PE.E store di the spring in equal to work done to compress the sprng.
This elastic P.E. stored in the sprng again convert into mechanical energy to move teh arms of the watch.
Question: 15
Does the hydrogen filled balloon possess any energy? Explain
Answer: 15
15-21
Yes hydrogen filled balloon possess potential energy
Explnation:
When a balllooon is filled with hydrogen
i- The gas particle will exert pressure on the walls of the balloon
ii- Work must be done by the hydrogen gas against the elastic force of the balloon walls.
iii- This work done is sotred in the form of elastic potential energy.
Hydrogen is thelightest gas and its density is lesser than air therefore.
* Balloon moves pward
* The net force acting on the balloon moves it upward against the gravity
* There fore its P.E. increases.
Question: 16
Does the tension in the string of swinging pendulum do any work? Explain.
Answer: 16
16-21
Not tension in the string of swininging pendulum does not perform any work.
Explnation:
Work is done when a body convers some displacement along the direction of the force.In swinging pendulum.
* The tension in a string is acting upward
* Displacement is perpendicular to the force of tension in the stirng.
* Therefore:
W = Fs cos 90 o
W= Fs (0)
W= 0
Question: 17
A man rowing boat upstreamis at rest with respect to shores, is he doing work?
Answer: 17
17-21
Not work is done as boat is at rest wiith respect to share.
Reason:
As boat is at rest with respect to shore so it covers no displament with respect to share.
Therfore d = 0
Since W = F d cos 0
W =f (0) cos 0 = 0
Question: 18
Does the tension in the string of a swinging pendulum do any work? Explain.
Answer: 18
18-21
No, it does not do any work
Reason: The tension in the string does not do work because it is always perpendicular to the covered path .
Since W = Fd cos 90 o
W = F d (0) = 0
Question: 19
A man drops a cup from a certain height, which breaks into pieces. What energy changes invpled?
Answer: 19
19-21
A cum throun from certain height losses its graivitatonal energy and gain its K.E. When it strikes the ground then a part of this inetic energy is use dto break the cup and rest of the gnergy onverts into.
1- Sound energy
2- K.E. of scaffered moving pieces
3- Heat Energy dissipated against friction
Question: 20
Why enery Severse are instead of normal bulbs?
Answer: 20
20-21
1- The consmptionof energy in nergy savers is far less than normal light bulb.
2- Energy saveres produces light of high power and intensity as compared to normal liht bulbs.
3- Energy savers prodcues very little amount of heat, while 98% of input is coveted into bheat is light bulbs.
Question: 21
A man rowing boat upstream is at rest with respect to shore, is he doing work?
Answer: 21
21-21
No, he is not doing any work with respect to the shore.
Explanation:
Since the man rowing a boat upstream is at rest w.r.r shore, therefore no displacemnet is covered, therefore no work is done by hik.
Mathematically;
W = FS cos 0
W= F(0) cos 0
W = 0