114 - Kinematics Questions Answers

Physics >> Mechanics part 1 >> Kinematics Medical Exam

a particle , with an inital velocity v0 in a plane , is subjected to a constant acceleration in the same plane . then in general ,

the path of the particle would be

1) circle

2) ellipse

3) parabola

4)   hyperbola

Asked By: SARIKA SHARMA
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Joshi sir comment

parabola 

for understanding this make components of v parallel and perpendicular to a

Physics >> Mechanics part 1 >> Kinematics Medical Exam

a train is moving with a velocity of 30m/s. When brakes are applied , it is found that the velocity  reduces to 10m/s in 240m.

When the velocity of the train becomes zero , the total distance travelled is??

270m   

Asked By: SARIKA SHARMA
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Joshi sir comment

by v2 = u2-2as

100 = 900-2*a*240

or 800 = 480a

or a = 80/48 = 10/6 = 5/3

so total distance upto rest is u2/2a = 900*3/2*5 = 270m

Physics >> Mechanics part 1 >> Kinematics Medical Exam

angle b/w vectors (i^+j^)and(j^+k^)  is

1) 60o

2) 90o

3) 300

4) 450

Asked By: SARIKA SHARMA
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Joshi sir comment

use the formula A.B = |A||B|cosθ

Physics >> Mechanics part 1 >> Kinematics Medical Exam

A at road of 200km & B at 100km road. A with vel 20m/s & B with 7.5m/s . Then wat will b d time when B overtake A.

1)  24s

2) 40s

3) 80s

4)nothing can be predicted

Asked By: SARIKA SHARMA
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Joshi sir comment

data are irrelevent

Physics >> Mechanics part 1 >> Kinematics Medical Exam

QUES A MAN RUNS AT A SPEED OF 4M/s  TO OVERTAKE A STANDING BUS . WHEN HE IS 6m  BEHIND THE DOOR (AT t=0) , THE BUS MOVES FORWARD & CONTINUES WITH A CONSTANT ACCELERATn OF 1.2m/s2 . the MAN SHALL GAIN THE DOOR AT TIME t EQUAL TO

A) 5.2s

b) 4.3s

c)2.3s

d)  the man shell never gain the door.

ans 4.3s , Sir ,on solving I 'm getting both 4.3 & 2.3 s ( when we solve sq root) so here i want to know why not the ans is 2.3s.      AMU 2012

Asked By: SARIKA SHARMA
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Joshi sir comment

After 2.3 sec. the man overtake the door first, in this time velocity of bus will be less than that of man so it is not possible to catch the bus then after 4.3 sec. the bus door will again reach to the man, in this time velocity of bus and man are same, so relative velocity is zero and catching of bus is possible. 

Physics >> Mechanics part 1 >> Kinematics Medical Exam

A BODY STARTS WITH INITIAL VELOCITY 30m/s & A RETARDATION OF 4m/s2 . FIND THE DISTANCE TRAVELLED BY THE BODY IN 8th SECOND.

ANS 1m

Asked By: SARIKA SHARMA
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Joshi sir comment

by v = u - at 

0 = 30 - 4t   implies t = 7.5

it means velocity will become 0 in 7.5 sec. 

distance covered in 7.5 sec. = 30*7.5 - 1/2*4*(7.5)= 225 - 225/2 = 225/2

distance covered in 7 sec. = 30*7 - 1/2*4*(7)2= 210 - 98 = 112

so distance covered in first half of eighth sec. = 112.5 - 112 = 0.5 m

distance covered in last half of eighth sec. = 0*0.5 + 1/2*4(0.5)2= 0.5

so total distance covered in eighth sec. = 0.5 + 0.5 = 1 meter

Physics >> Mechanics part 1 >> Kinematics Medical Exam

A TOY CAR TRAVELS FROM A TO B AT A CONST. SPEED OF 20 km/h & IMMEDIATELY RETURNS TO A AT A CONST. SPEED v.  IF THE AVG. SPEED OF THE CAR IS 24 km/h . THEN v IS = ?

Asked By: SARIKA SHARMA
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Joshi sir comment

total distance = d+d = 2d km.

total time taken = d/20 + d/v hours

so avg. speed = 2d/[d/20 + d/v]

or 24 = 2/[1/20 + 1/v]

or 12 = 1/[1/20 + 1/v]

or 1/20 + 1/v = 1/12

or 1/v = 1/12 - 1/20

or 1/v = 2/60

or v = 30

A hunter aims his gun at a monkey sitting on a tree at the instant bullet leaves the gun the monkey drops down . WILL  THE  BULLET  HIT  THE  MONKEY  ?

Asked By: PRIYANKA DAHIYA
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Joshi sir comment

yes because monkey and bullet both are falling with the same gravity

Physics >> Mechanics part 1 >> Kinematics Medical Exam

IN QUESTn < B/W 2 NON ZERO VECTOR A &B 120* RESULTANT GIVEN IS GREATER WHILE ACC. TO IT SHD BE LESS SO I REQUEST  YOU SIR TO AGAIN CHECK . QUES FROM HC  VERMA

Asked By: SARIKA
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Joshi sir comment

i am confirmed, option B will be correct answer

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.

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