Physics MCQs thread.

[arlery]

But how'd you solve it?

 

[xHazeMx]

But how'd you solve it?

basically, u have
S = 1000 m ( 1 km )
a = 0.2 ms^-2
V = 0 m/s (as it stops after braking)
and u need to find (U) .. which is the initial speed ( the safe speed )
put the values in the equation
V^2 = U^2 + 2 a S
0 = U^2 - ( 2 x 0.2 x 1000 ) .................. ( the minus sign indicates the deceleration )
U^2 = 400
U = 20 m/s , so the answer is A

 

[Saturation]

how can I solve this? =$

It's just like any other speed, time ,etc. question! the distance between the yellow and red signs is 1000m , the train is decelerating at 0.2m s^-2 , and it stops when it reaches the red sign, so:

s = 1000
a = -0.2
v = 0
u = ? ( the maximum safe speed"

use the formula : v^2 = u^2 + 2as , and find "u"

hope that helped!

 

[arlery]

Yeah I got it. Thanks !

 

[arlery]

Why is the answer A?

 

[xHazeMx]

Why is the answer A?

speed of approach = speed of separation
speed of approach = u - ( -u) = 2u
speed of approach = 5/3 u - (- 1/3 u ) = 2u ( this is the only choice which will give u the right answer ) .. A

 

[abdullah181994]

help plz ,explian it ans is B

 

[abdullah181994]

plzzzzzzzzzzzzzzzzzz expliannnnn plzzzzzzzzzzzzz :crazy: :%)

 

[abdullah181994]

explian this plz i am confused . :crazy: :%) =@
thanks .

 

[xHazeMx]

help plz ,explian it ans is B

when the weight is added. surface Z contracts (compression) and Y stretches (tension) as the upper rod is bent. similarly with X, the surface containing X stretches so its is tension.

 

[xHazeMx]

plzzzzzzzzzzzzzzzzzz expliannnnn plzzzzzzzzzzzzz :crazy: :%)

the phase difference between the molecules in a stationary wave is 180 degrees. so as u leave one node, the molecules should move in the opposite direction. now see the graph at A the longest arrow shows an antinode and the dot shows a node. in figure A, there are 2 antinodes ( 2 of the longest arrows ) and two dots ( nodes ) . so the answer is A

 

[abdullah181994]

 

[ShootingStar]

please explain my doubts someone.. on page 41..

 

[unique840]

doubts!!

iska ans A hai? mene to jo b kiya hai maths k M1 k formula se kiya hai

 

[abdullah181994]

doubts!!

is the answer B

 

[yubakkk]

how 2 do it??

 

[ShootingStar]

doubts!!

iska ans A hai? mene to jo b kiya hai maths k M1 k formula se kiya hai

haan A hai... method to batao..

 

[ShootingStar]

And my other doubt is the same as the one asked by yubakkk.. the answer is B btw

 

[arlery]

Yeah I have the same doubt as yubakkk.

 

[hassam]

see...F=qV/D...F=ma
qV/D=ma.....let V/D--->> A constant K....SO ma=Kq...rearranging....a=Kq/m....means a is proportional to q/m ratio....now chill out...apply this nd u ll get B