Physics MCQs thread.

[Zishi]

howw

It's according to newton's 3rd law of motion. Use it. The force applies by a body of large mass by a small mass is equal to force applied by body of large mass on body of small mass.

 

[xHazeMx]

howw

initially, F acts on the whole body which is m + 2m = 3m
so, F = 3ma, make (a) the subject as (a) is constant, u will get a= F/3m
now F acting on 2m ( object Y )

F= 2ma
F= 2m (F/3m)
force acting on object Y = 2F/3 , so ans is D

 

[farrukh]

C?

 

[Sannikutti]

Hi
i had a doubt
A car of mass 1000kg first travels forwards at 25ms
and then backwards at 5ms
What is the change in the kinetic energy of the car?
A 200kJ B 300kJ C 325kJ D 450kJ

 

[arlery]

Find both the kinetic energies and subtract them. The answer you get will be 300kJ

 

[Xthegreat]

Hi
i had a doubt
A car of mass 1000kg first travels forwards at 25ms
and then backwards at 5ms
What is the change in the kinetic energy of the car?
A 200kJ B 300kJ C 325kJ D 450kJ

ans : B?

 

[yubakkk]

Hi
i had a doubt
A car of mass 1000kg first travels forwards at 25ms
and then backwards at 5ms
What is the change in the kinetic energy of the car?
A 200kJ B 300kJ C 325kJ D 450kJ

change =0.5*m*(25^2-(-5)^2

 

[Xthegreat]

Can anyone please explain Question 12 and Question 22? http://www.xtremepapers.me/CIE/Internat ... 2_qp_1.pdf
Please explain.

Q12

the eqn u should have is 60m - 30m = 2mv
* it should b a MINUS because both objects r travelling in opposite directions.
* 2mv because both objects join together after impact making their total mass 2m and their speed the same v.
ans: A

 

[yubakkk]

plz explain :%)

f=mg
so 2g-6=10a because both mass will move
sa a=1.4 option a

 

[Xthegreat]

And another one


A projectile is launched at 45° to the horizontal with initial kinetic energy E.
Assuming air resistance to be negligible, what will be the kinetic energy of the projectile when it
reaches its highest point?
A 0.50 E
B 0.71 E
C 0.87 E
D E


since it is 45' to the horizontal, meaning the vertical velocity = horizontal velocity ( cos45=sin45)
we all know that the horizontal velocity is always the same and never changes throughout the motion
and we also know that the vertical velocity will decrease to zero by the time it reaches it's max point.
the total KE would be the KE of horizontal + vertical
since the vertical has decrease to zero, the KE would be half less than before making the answer A.

 

[nidzzz09]

A parallel beam of light of wavelength 450 nm falls normally on a diffraction grating which has
300 lines /mm.
What is the total number of transmitted maxima?
A 7
B 8
C 14
D 1



THANKS

 

[xHazeMx]

A parallel beam of light of wavelength 450 nm falls normally on a diffraction grating which has
300 lines /mm.
What is the total number of transmitted maxima?
A 7
B 8
C 14
D 1



THANKS

A

 

[nidzzz09]

Can yu plz show the workin

 

[yubakkk]

for hatexam q. about moment
hey hatexam
u r still confuse to take moment
remember the distance u have to take must be perpendicular from line of action of force and point from where u have taken moment
s lets take moment about cg ie middle w
so both f has clockwise moment and down w has anticlock
so applying principal of moment
clock=anticlock so
f*h/2+f*h/2=w*a
so option a match
also u can take moment on down f
it is f*h=wa similar 2 option a
also u can take moment on upper f
it is f*h+w*a=w*2a so simailar 2option a
now where i ur confuse tellme///
sorry for dat i m unable 2 make u clear in first explanation so i have wrtten this full xplain..
hope u r clear are u?

 

[yubakkk]

Can yu plz show the workin

d=1/300 *10^"-3
max orde fall on 90 degree so dsin 90=n*lamda
so u can get n=ans

 

[ShootingStar]

Please answer my question on page 68

 

[yubakkk]

Please answer my question on page 68

x=lamda D /a
so D IS TWICE AND A IS HALF SO X WILL INCREASE BY 4 TIMES
SO X=16
ANS D

 

[airborne1944]

Help me guys. Please Explain....

Q21 http://www.xtremepapers.me/CIE/Internat ... 5_qp_1.pdf

 

[yubakkk]

Help me guys. Please Explain....

Q21 http://www.xtremepapers.me/CIE/Internat ... 5_qp_1.pdf

this link says page not found

 

[yubakkk]

http://www.xtremepapers.me/CIE/Internat ... _qp_11.pdf
any one help q.5 q.22 any 34
plzplpzlplz[;z