Physics question and answer on motion

Physics question and answer on motion 1

A car moves from rest with an acceleration of 0.2m/s2. Find the velocity when it has moved a distance of 50m.

Answer

V2 + u2 = 2aS

Where v = ?, u = 0 (because the car started from rest) a = 0.2m/s2, and  = 50m

V2  + 02 = 2 x 0.2 x 50

V\quad =\sqrt { 20 } =4.47m/{ s }^{ 2 }

Physics question and answer on motion 2

A car has a maximum velocity of 108km/h. How far does it travel in ½minute?

Answer

V\quad =\frac { s }{ t } \quad

Where v = 108m/h, s = didtance and t = 0.5minute = 0.5 x 60 = 30s

108km/h=\frac { 108\times 1000 }{ 60\times 60 } =\frac { 108000 }{ 3600 } =30m/s

S = V x t = 30 x 30 = 900m

S = 900m (distance traveled)

Physics question and answer on motion 3

A lorry travels at an average of 90km/h. What distance does it cover in 4 seconds?

Answer

speed\quad =\frac { distance\quad  }{ time }

speed =90km/h = 25m/s, t = 4seconds

distance = speed x time = 4 x 25 = 100m

distance covered = 100m

Physics question and answer on motion 4

A car accelerates uniformly at 2m/s2 for 3 minutes, what is the velocity of the car?

Answer

a\quad =\quad \frac { v }{ t }

V = at

Where a = 2m/s2, t = 3 x 60 = 180 seconds

V = 180 x 2 = 360m/s

Physics question and answer on motion 5

A train slows from 108km/h with a uniform retardation of 5m/s2. How long will it take to reach 18km/h, and what is the distance covered.

Answer

u=108km/h\quad =\frac { 108\times 1000 }{ 60\times 60 } =30m/s,\quad (Initial\quad Velocity)\quad \\ \\ V=18km/h\quad =\frac { 18\times 1000 }{ 60\times 60 } =5m/s\quad (Final\quad Velocity)

Retardation = negative acceleration a = -5m/s2

Uisng

V = U + at

at = V-U

t\quad =\quad \frac { V-U }{ a } =\frac { 5-30 }{ -5 } =\quad \frac { -25 }{ -5 } =\quad 5s

To obtain the distance covered use

S = ut +½at2

Where u = 30m/s, t = 5s = a = -5m/s2 and S=?

S = 30 x 5 + ½ x -5 x 52

S = 150  +  0.5 x -5 x 25 = 87.5m

Physics question and answer on motion 6

which of these motions is a uniform?

(a)Molecular motion (b). Circular motion (c).Vibrating pendulum

Answer: B

Physics question and answer on motion 7

Define the followings:  (a).Scale quantity and (b) Vector quantity

Answer

(a).Scale quantities are those quantities that have only magnitude but no direction

(b).Vector quantity is defined as the quantity that have but magnitude and direction

Physics question and answer on motion 8

List form equations of motion

Answer

V =U + at

S = Ut +½at2

V2 + U2 + 2aS

S=(\frac { V\quad +\quad U }{ 2 } )t

Physics question and answer on motion 9

Which of these is not correct?

A. Distance is a scalar quantity. B Velocity is a vector quantity. C speed is a vector quantity. D. Displacement is a vector quantity.

Answer: C

Physics question and answer on motion 10

Which of these is not correct?

A.Initial velocity of a body released from rest is zero

B.Final velocity of a body thrown up vertically is zero

C.Initial velocity of a body dropped from top is zero

D.None of the above

Answer: D

Physics question and answer on motion 11

Which of these equations of motion is correct?

  1. v = u –at  B.  a = tv   C.  V= at –u    D. v = u + at

Answer: D

Physics question and answer on motion 12

Which of these is not example of scalar quantity?

  1. Speed B. distance C. temperature D. Velocity

Answer: D

Physics question and answer on motion 13

Which of these causes motion?

  1. acceleration B. speed C. velocity  D. force

Answer: D

Physics question and answer on motion 14

Which of these are two types of forces?

  1. contact and electric field force B. gravitational and electrical force  C. contact and field force   D. earthquake and volcanic force

Answer: C

Physics question and answer on motion 15

What a body falls to ground once again, what is it height above the ground?

A.1 B. 2 C. 0 D. none of the above

Answer: C

Physics question and answer on motion 16

A body travels from rest with acceleration 8m/s2.  Find its velocity when it has covered a distance of 100m

Answer

v2 = u2  + 2as

v = ?, u = 0 (since it started from rest), a = 8m/s2 and s = 100m (distance)

v2 = 02 + 2 x 8 x 100

v2 = 1600

v = 40m/s

Physics question and answer on motion 17

An object falls from a height of 20m. What is its velocity just before hitting the ground?  Take acceleration due to gravity g = 10m/s2

Answer

v2 = u2 + 2gs

v = ?, u = 0 ( when an object falls from a height), g = 10m/s2 and s = 20m (distance)

v2 = 02 + 2 x 10 x 20

v2 = 400

v = 20m/s

Physics question and answer on motion 18

A ball thrown vertically upwards from ground level hits the ground after 4s. Calculate the maximum height it reached during its journey ( g = 10/s2)

Answer

To calculate this, note that distance from downward to upward is equal to distance from upward to downward.

S = ut +  ½gt2

S=?, u =0 (when a body falls from up), g = 10m/s2 and t = ½ of 4 = 2s

S = 0 x 2 + ½ x 10 x 22

S = 0 + ½ x 10 x 4

S = 20m

Physics question and answer on motion 19

If a stone of 20g and a feather of 2g are dropped from a height. Which of them will reach the ground first if they fall under the influence of gravity alone?

Answer: the two will reach the ground at the same time

 

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