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| Physics mcqs |
Physics MCQs
with explanation & examples
MCQs #1
Newton's _______ law of motion is also called definition of Inertia.
A. first law of motion
B.Second law of motion
C.third law of motion
D. none of them
Answer: A
MCQs #2
Two vectors are added by _________rule.
A. Right hand rule
B. left hand rule
C.tail to tail rule
D. Head to tail rule
Answer: D
MCQs #3
If the magnitude of two vectors is the same as the magnitude of their addition (i.e |A|=|B|=|A+B|) then the angle between them will be_____.
A. 45 degree
B. 60 degree
C.120 degree
D.90 degree
Answer: 120 degree
Explanation; Let A=B=2 units and angle is 120 degree, then
|A+B|=√A^2+b^2+2ABcostheta
|A+B|=√4+4+2x2x2cos120 [ cos120=-1/2]
|A+B|=√4+4-8/2
|A+B|=2;
Hence
|A|=|B|=|A+B| proved.
MCQs #4
In projectile motion when maximum range is doubled then velocity will be _____.
A.multiplied by square root of 2
B. will be divided by square root of 2
C.will be multiplied by 2
D. will be divided by 2
Answer:A
explanation: let velocity is 2 m/s and g=10 then
Range(max)= v^2 sin2theta/g
=0.2
Now let velocity= √2 x 2 all other data is same
Range(max)= (√2x2)^2 sin2x45/10
= 0.4 hence range is doubled.
MCQs #5
What is average density of earth?
A.5000 kg/m^3
B.5500 kg/m^3
C.4000 kg/m^3
D.4500 kg/m^3
Answer:B
MCQs #6
For a point at the same distance above the surface and below the surface, the acceleration due gravity will decrease more_____.
A.Above the surface
B.Below the surface
C.Same at both points
D. none of them
Answer:A
Explanation: According to relation,
Change in acceleration due to gravity above the surface; g'=g(1-2h/R)
where h=height g=9.8 m/sec^2 and R=radius of earth
and
Change in acceleration due to gravity below the surface; g'=g(1-d/R) here d=depth;
Now in height relation there is 2 in numerator that means it will be greater value in numerator in height relation than the depth relation when both height and depth are taken same value;Now obviously when we subtract greater value from 1 it will give us lesser value and when lesser value is multiplied with g it will produce smaller value hence a point at the same distance above the surface and below the surface, the acceleration due gravity will decrease more at height than the depth.
MCQs #7
When an elevator goes up with uniform velocity then the apparent weight will be_____.
A.increase by ma
b.decrease by ma
C.remain same as original weight
D.increase by 2ma.
Answer:C
According to formula ;
Apparent weight=original weight+ma (here m=mass,a=Acceleration when abody goes up or down)
According to given condition acceleration is zero because of uniform velocity.
hence,
Apparent weight=original weight+mx0
apparent weight=Original weight
proved..
MCQs #8
If wavelength of a wave is 12m the first anti-node will be at_______.
A.3m
B.4m
C.6m
D.0m
Answer: A
Explanation:
First anti-node is equal to wavelength/4 hence 12/4 is equal to 3m..
MCQs #9
If a ball is thrown in projectile motion at 60 degree it goes to a certain range, at what other angle the projectile will arrive at the same range.
A.25 degree
B.30 degree
C.45 degree
D.55 degree
Answer:B
Explanation: When a body is thrown in projectile motion, there are two possible angles that will reach at same range except when angle is 45 degree.cbody is thrown at certain angle the difference between that angle and 45 degree will be added or subtracted from 45 degree.
for example: If you have given 60 degree, here we can see that difference between 45 and 60 is of 15 degree Now we will subtract this 15 degree from 45 so we will get 30 degree this is other possible degree that will reach at same range and if we were given 30 degree then we would add 15 degree to 45 so we got 60 degree.
TIP
If degree is given above the 45 then difference value will be subtracted and if we have given value less than 45 then we will add the difference value.
MCQs # 10
Who discovered the value of G=6.67 x 10^-11 m3 kg-1 s-2?
A.Newton
B.Maxwell
C.Faraday
D. none of them
Answer D: it is Cavendish.
MCQs # 11
Which fringe is not possible in young's double slit experiment?
A.Zeroth bright fringe
B.1st bright fringe
C.1st dark fringe
D.Zeroth Dark fringe
Answer:D
MCQs # 12
A lens aberration in which multicoloured blurredimage is formed is called____?
A.Spherical aberration
B.Chromatic Aberration
C.Concave Aberration
D. none of them
Answer:B
Explanation: It's definition.
MCQs # 13
The periodic alternations of sound between maximum and minimum loudness is called ______.
A.Pitch of sound
B.frequency of sound
C.Beats of sound
D.Quality of sound
Answer:C
Explanation: It's definition
MCQs # 14
1 torr is equal to to:
A.13.3 N/m^2
B.1.33 N/m^2
C.133.3 N/m^2
D.0.133 N/m^2
Answer: C
MCQs # 15
Kilo watt-hour is unit of;
A.Power
B.Work
C.Energy
D.both B&C
Answer: D
Explanation: Power=Energy/time
hence Energy=Power x time
putting their units
Energy= Kilo watt x hour
This is also unit of work because power is also defined as rate of doing work
(i,e Power=work/time).
