302 - Mechanics part 1 Questions Answers

Physics >> Mechanics part 1 >> Kinematics Medical Exam

Q A CURVE IS REPRESENTED BY y=sinx IFx IS CHANGED FROM PIE/3 TO PIE/3+PIE/100, FIND APPROX. CHANGE IN x?

Q  A CAR IS GOING DUE NORTH AT A SPEED =50km/h IT MAKES A 90* LEFT TURN WITHOUT CHANGING SPEED THE CHANGE IN VEL. OF CAR IS=?                                                                                                  (ANS 70km/h towards south west )  i want to know that here we are  just changing the directn so only directn. shd. b change but here magnitude is also changing HOW?

FLUIDS

Q A BAROMETER KEPT IN N ELEVATOR READS 76cm WHEN IT IS AT REST . IF ELEVATOR GOES UP WITH INCREASING SPEED READING WILL BE <76 cm . IS REASON IS THAT PRESSURE IS DIRECTLY PROPTn TO HEIGHT ?

Asked By: SARIKA
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Joshi sir comment

I think we have to caculate change in y

since y = sin x

so dy = cosx dx = cosπ/3* π/100 = π/200

 

the initial velocity of car = 50j      and after turn velocity = -50i                              here i and j are the unit vectors along east and north direction

so change in velocity = -50i - 50j

its mod = 50 √2 = 70

 

Because in barometer the extra Hg level will experience a downward force so Hg level will decrease.

Physics >> Mechanics part 1 >> Kinematics Medical Exam

Q A VECTOR A POINTS VERTICALLY UPWARD & B PTS. TOWARDS NORTH. VEC. PRODUCT ACROSS B IS ALONG WHICH DIRECTION?

Q LET < B/W TWO NON ZERO VECTORS A &  B BE 120* &  ITS RESULTANT BE C THEN

1) C MUST BE EQUAL TO MOD. OF A-B

2) C MUST BE LESS THAN MOD. OF A-B

3)C MUST BE GREATER THAN MOD. OF A-B

4)C  MAY BE EQUAL TO MOD. OF A-B  

Asked By: SARIKA
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Joshi sir comment

Take your right hand fingers along A and curl these fingers along B, thumb will give you an idea for A × B. for the given problem answer will be west.

 

|A+B|2 = |A|2 + |B|2+ 2A.B            (1) 

|A-B|2 = |A|2 + |B|2 - 2A.B             (2)

on subtracting (2) by (1)

|A+B|2 - |A-B|= 4A.B

so C2 = |A-B|+ 4A.B

or C2 = |A-B|2 +4|A||B|cos120

since cos120 is negative so C will be less than |A-B|  

Q E=ELECTROMAG F, G=GRAVT.F, N = NUCLEAR F B/W 2 e- AT A GIVEN PTN. THEN E>G>N HOW=?  BECAUSE G< THEN OTHER FORCES.

Asked By: SARIKA
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Joshi sir comment

for the distance upto fermi level order will be N>E>G

but  the distance between electrons is greater than fermi level so the given order is justified because now nuclear forces will be very weak.

Physics >> Mechanics part 1 >> Kinematics Medical Exam

Q A PARTICLE START MOVING FROM REST STATEVALONG A STRAIGHT LINE UNDER ACTION OF A CONST. F & TRAVEL DIST. X IN FIRST 5 sec THE DIST. TRAVELLED IN NEXT 5 sec WILL BE=?

QA CUBE OF A SIDE a IS HEATED TO RAISE ITS TEMP. BY 3*C IF Y IS COEFF. OF VOL. EXPANSION THEN TOTAL INCREASE IN AREA=? (ANS 12Yasqure. )

 WAVES & OCILL.                 Q OBSV. IS MOVING TOWARDS A SOURCE AT REST WITH 30m/s if sound is sounding a sound of freq 500Hz & speed of sound is 300m/s then wavelenth by obsv. =?

Q TEMP. OF GAS INCREASED BY 2K KEEPING PRESS. CONST. SPEED OF SOUND IN GAS=?    ans=1.22m/s

Q THE MASS OF ELEVATOR = 4000kg .STARTING FROM REST HOW MUCH DIST. WILL IT RISE IN 2s IF TENSION =56 kN .  I want to know why we use ,' a ' for cal. dist. why 'a+g' is NOT use.

Asked By: SARIKA
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Joshi sir comment

 

by formula s = ut + 1/2 a t2

u = 0 [given]

so       s = 1/2 a (5)2= 25a/2       for first 5 sec.

and    s = 1/2 a (10)2 = 50a        for total 10 sec. from start

so for next 5 sec. distance = 50a - 25a/2 = 75a/2

 

answer :  a'3 = a3 (1+ γ3)     here a' is the side of the cube after heating it

so a' = a (1+3γ)1/3

so area increment = 6a'2 -  6a2 = 6a2 [(1+3γ)2/3 - 1] = 6a2 [ 2γ] = 12γa2

Please submit all the questions seperately. 

 

λ = v/n = 300/500 

 

i think you are asking about increment in speed

so according to formula v'/v  = [(T+2)/T]1/2 

or v'/v = 1 + (1/T)

so v' - v = v(1/T) = 332*1/273 =  1.22       here 332 is the speed of sound at 273K

 

 

when a machine works , you should not count gravity, for example if we raise our hand upword with uniform velocity then gravity makes no problem in it because our hand is working by our internal capabilitites

 

 

 

Physics >> Mechanics part 1 >> Kinematics Medical Exam

Q A PARTICLE STARTS MOVING WITH ACC.=2m/s 2  DISTANCE TRAVELLED BY IT IN 5th HALF SECOND IS=?

 

 

 

Q A PARTICLE  MOVES IN A STRAIGHT LINE & ITS POSITION X  AT TIME t IS GIVEN BY X RAISED TO P. 2=2+t . ACC.   IS GIVEN BY=?                                                                                                                                                (ans . -2/4t cube)

Asked By: SARIKA
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Joshi sir comment

first calculate distance of 4 seconds by using s = ut + 1/2 a t2

then distance of 4.5 sec. by same formula 

difference of these 2 is the distance of 5th half sec.

but some writter consider 5th half as 1/2 +1/2+1/2+1/2+1/2 means 2.5

so they use the same formula first for 2 sec then for 2.5 sec, then their difference.

according to my opinion first is more true way to solve.

Dear Sarika please submit only one question in a box, for a new question use another box so that i could give answers more quickly.

 

According to the given condition

x2 = 2+t

on differentiaing we get 2x dx/dt = 1

or v = 1/2x

now differentiate it again we get dv/dt = -(1/2x2 )(dx/dt) = -(1/2x2 )(-1/2x) = 1/4x3                                  

  

sir,  can u please post a topic on rigid body rotation ? mainly heip to solve question please.  with some examples.

Asked By: SHUBHAM VED
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Joshi sir comment

Yes, I will do very soon.

there is a small block of mass m kept at the left end of a larger block of mass M and length l.The system can slide on a horizontal road.The sysytem is started towards right with an initial velocity v. The friction coefficeient between the road and the bigger block is μ and that between the block is μ/2. Find the time elapsed before the smaller block separates from the bigger block?

Asked By: AMIT DAS
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Joshi sir comment

Since there is no force for accelerating the larger block so larger block will be retarded due to this smaller block will move in forward direction 

for the process equations are 

0 + (µ/2)mg - µ(M+m)g = Ma   (1)

(µ/2)mg - ma = ma1                 (2)

take the value of a from eq (1) to eq (2) and get a1

then l = 0t + (1/2)a1 t2

 

 

a wedge of mass M' is connected with a hanging block of mass M with a light string and a massless pulley. and a small block of mass m is placed on the top of te wedge. find the mass M of the hanging block which will prevent the smaller block from slipping over the wedge . All the surfaces are smooth .

Asked By: AMIT DAS
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Joshi sir comment

 

According to the given diagram       Mg - T = Ma,             T = (M'+m)a       and           macosθ = mgsinθ        

solve these equations.

 

please solve  q. no. 33 on page no. 82 of hc verma  (part -1 newtons laws of motion)......

Asked By: AMIT DAS
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Joshi sir comment

Dear Amit 

this book is not available here so please send the question. 

Why earth moves in orbital motion around the sun ...? why not in circular motion...? 

Asked By: HARISH
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Joshi sir comment

Since every heavenly body like sun, earth, moon are rotating freely in free space, there is no body which is placed on a base, so rotation of every body depends on all the surrounding bodies. It means its track will also depend on the attraction forces given by all the surrounding bodies. 

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