Important Questions and answers on Motion for Class 9 physics

Match the column

Question 1

column A	Column B
The Slope of the speed-time graph is called	Average Velocity
The arithmetic mean of initial and final velocity	speed
What quantity is obtained by the area under speed time graph	acceleration
The slope of the distance time graph	distance

Answer

column A	Column B
The Slope of the speed-time graph is called	acceleration
The arithmetic mean of initial and final velocity	Average Velocity
What quantity is obtained by the area under speed time graph	distance
The slope of the distance time graph	speed

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Question 2

Match the column

Column A	Column B
Speed	Scalar
Distance	Vector
Displacement
Acceleration
Velocity

Answer

Scalar : Speed ,distance
Vector: Velocity,Acceleration ,displacement

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Question 3
Match the column

Column A	Column B
22 km/h	.266 m/s
100 Km/h	6.11 m/s
10 m/min	27.77 m/s
2 km/s	83.33 m/s
5 km/min	2000m/s

Answer

22 km/h=6.11 m/s
100 Km/h=27.77 m/s
10 m/min= .266 m/s
2 km/s=2000 m/s
5 km/min=83.33 m/s

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Table type question

Question 4
A car moves in a straight line from rest at t=0. It accelerates with $2m/s^{2}$ . Solve the following table

Time	2 sec	?	?	10 min
Displacement	?	?	25 m	?
Velocity	?	10 m/s	?	?

Answer

Time	2 sec	5 sec	5 sec	10 min
Displacement	4 m	25m	25 m	14.4 km
Velocity	4m/s	10 m/s	10 m/s	240m/s

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Short Answer Type

Question 1
An air-plane accelerates down a runway at 3.20 m/s² for 32.8 s until is finally lifts off the ground. Determine the distance travelled before take off.

Answer

Given,
the initial velocity = 0 m /s,
acceleration = 3.20 m/s²,
t = 32.8 s
This is quite a basic question of 2nd equation of motion
$s=ut + \frac {1}{2}a t^2$
s = 1/2 at²

s=(.5)(3.20)(32.8)²= 1721.344m

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Question 2
A Jeep starts from rest and accelerates uniformly over a time of 5.21 seconds for a distance of 110 m. Determine the acceleration of the Jeep.

Answer

Use 2nd equation of motion
$s=ut + \frac {1}{2}a t^2$
110 = [0.5a × (5.21)²2]
a = 110 / (5.21²2 × 0.5)
a = 8.10m/s²

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Question 3
John is riding the Giant Drop at Canada. If John free falls for 2.6 seconds, what will be his final velocity and how far will he fall?

Answer

Using 1st equation
v=u+at
v=gt where g =acceleration due to gravity=9.8 m/s²
v=9.8X 2.6=25.48 m/s
Using 2nd equation
$s=ut + \frac {1}{2}a t^2$
$s=\frac {1}{2}g t^2$
s=33.124m

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Question 4
A racing car accelerates uniformly from 18.5 m/s to 46.1 m/s in 2.47 seconds. Determine the acceleration of the car and the distance travelled.

Answer

$a =\frac {(v-u)}{t}$
$a=\frac {(46.1-18.5)}{2.47}$
a=11.47m/s²

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 Question 5
A feather is dropped on the planet other than earth which has very low acceleration due to gravity from a height of 1.40 meters. The acceleration of gravity on the other planet is 1.67 m/s². Determine the time of feather to fall to the surface of the other planet

Answer

Here u=0, a=1.67m/s² , s=1.40 , t=?
Using 2nd equation
$s=ut + \frac {1}{2}a t^2$
t= 1.29 s

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Question 6
Rocket-powered sleds are used to test the human response to acceleration. If a rocket- powered sled is accelerated to a speed of 444 m/s in 1.8 seconds, then what is the acceleration and what is the distance that the sled travels?

Answer

Here u=0, v=444m/s ,t=1.8
$a= \frac {v-u}{t} = \frac {444}{1.8}=246.66 m/s^2$ Now
$s=ut + \frac {1}{2}a t^2$
s=399.6 m

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Question 7
Honda Activita accelerates uniformly from rest to a speed of 7.10 m/s over a distance of 35.4 m. Determine the acceleration of the bike.

Answer

Here v=7.10 m/s , s=35.4 m ,u=0 ,a=?
Now,
$v^2 =u^2 + 2as$
a=.712 m/s²

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Question 8

An Aeronautics engineer is designing the runway for an airport. Of the planes that will use the airport, the lowest acceleration rate is likely to be 3 m/s². The take off speed for this plane will be 65 m/s. Assuming this minimum acceleration, what is the minimum allowed length for the runway?

Answer

Here v=65 m/s , s=? ,u=0 ,a=3m/s²
Now,
$v^2 =u^2 + 2as$

distance= 704m

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Question 9

A BMW car travelling at 22.4 m/s skids to a stop in 2.55 s. Determine the skidding distance of the car (assume uniform acceleration)

Answer

u = 22.4 m/s,v = 0, t = 2.55 s
using First equation of motion
v = u+at
0 = 22.4+aX2.55
a = -8.784 m/s²

Now using third equation of motion
$v^2=u^2 +2as$
0=(22.4)² -2X8.784Xs
s=28.56m

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 Question 10
A kangaroo is capable of jumping to a height of 2.62 m. Determine the take off speed of the kangaroo.

Answer

Here v=0 , s=2.62m ,u=? ,a=-9.8 m/s²
Now,
$v^2 =u^2 + 2as$

u= 7.17m/s

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Question 11
If Rahul has a vertical leap of 1.29 m, then what is his take off speed and his hang time (total time to move upwards to the peak and then return to the ground)?

Answer

Here v=0 , s=1.29m ,u=? ,a=-9.8 m/s²
Now,
$v^2 =u^2 + 2as$
u= 5.03m/s.
Now time going Up,
v=u+at
or
t=-u/a = 5.03/9.8 =.513 s
Total hang time = 2 * .513 =1.03s

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Question 12
A bullet leaves a rifle with a muzzle velocity of 521 m/s. While accelerating through the barrel of the riffle, the bullet moves a distance of 0.840 m. Determine the acceleration of the bullet (assume a uniform acceleration).

Answer

Here v=521 m/s , s=.840m ,u=0 ,a=-?
Now,
$v^2 =u^2 + 2as$
$a = 162 \times 10^3$ m/s²

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Question 13
A baseball is popped straight up into the air and has a hang- time of 6.25 s. Determine the height to which the ball rises before it reaches its peak. (Hint: the time to rise to the peak is one- half the total hang-time.)

Answer

Time to rise = 6.25/2= 3.125 s s=? ,a =9.8 m/s² Now,
$s= \frac {1}{2} at^2$
s= 47.9m

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Question 14
The observation deck of the tall skyscraper 370 m above the street. Determine the time required for a penny to free fall from the deck to the street below.

Answer

s=370m ,a =9.8 m/s² Now,
$s= \frac {1}{2} at^2$
t= 8.69s

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Question 15
A bullet is moving at a speed of 367 m/s when it embeds into a lump of moist clay. The bullet penetrates for a distance of 0.0621 m. Determine the acceleration of the bullet while moving into the clay. (assume a uniform acceleration.)

Answer

u=367 m/s ,a =? , s=.0621 m,v=0
Now,
$v^2 =u^2 + 2as$
$a = -1.08 \times 10^6$ m/s² (Negative sign shows deceleration)

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Question 16
A coin is dropped into a deep well and is heard to hit the water 3.41 s after being dropped. Determine the depth of the well.

Answer

depth of well= 57.0 m

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Question 17
It was once recorded that a Jaguar left skid marks that were 290 m in length. Assuming that the Jaguar skidded to a stop with a constant acceleration of -3.90 m/s²  , determine the speed of the Jaguar before it began to skid.

Answer

speed= 47.6 m/s

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Question 18
A plane has a take off speed of 88.3 m/s and requires 1365 m to reach that speed. Determine the acceleration of the plane and the time required to reach this speed.

Answer

acceleration = 2.86 m/s²
time= 30.8s

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Question 19
A dragster accelerates to a speed of 112 m/s over a distance of 398 m. Determine the acceleration (Assume uniform) of the dragster.

Answer

acceleration = 15.8 m/s²

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Question 20
With what speed in miles/ h (1 m/s= 2.23 mi/hr) must an object be     thrown to reach a height   of 91.5 m (equivalent to one football field)? Assume negligible air resistance.

Answer

v=0 (at maximum height),u=?,h=91.5m ,g=9.8m/s²
From 3rd equation of motion
$v^2-u^2=2gh$
Substituting and solving, we get
$u=\sqrt (2gh)$
=42.34m/s
=94.43 miles/hr

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Long answer Type

Question 21
A Truck starting from rest moves with a uniform acceleration of 0.2 m /s² for 2 minutes. Find
(a) the speed acquired
(b) the distance travelled.

Answer

a=0.2 m /s², t=2 min=120 s, u=0
$v=u+at$
v=24 m/s
$s=ut+ \frac {1}{2}at^2$
s=1440 m

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Question 22
Study the speed time graph


Find following based on the graph
a) Which paths have constant speed
b) when is the maximum speed reached
c) when is the acceleration happened
d) when is the deceleration happened

Answer

a) AB and DE
b) C
c) OA and BC
d) CD

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Question 23.
What does the odometer of an automobiles measure? Under what condition is the magnitude of average velocity of an object equal to its average speed?

Answer

a. Odometer is a device that measures the distance travelled by an automobile based on the perimeter of the wheel as the wheel rotates. b. Average speed is equal to the magnitude of average velocity When an object moves along a straight line in the same direction. In this case its total path length is the magnitude of displacement.

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Question 24.
(a) What is the quantity which is measured by the area occupied below the velocity time graph?
(b) A train starting from rest attains a velocity of 72 km/h in 5 minutes. Assuming that the acceleration is uniform, find out the
(i) acceleration
(ii) the distance travelled by the train for attending this velocity?

Answer

a. Displacement
b. v=72 km/hr =20 m/s , u=0 ,t=5 min=360 sec
$v=u+at$
a= .05 m/s²
$s=ut+\frac {1}{2}at^2$
s=3240 m

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Question 25.
(i)State Newton’s 1st law of motion? (ii)Why is it called as law of inertia? Define inertia? (iii)On what factors does inertia depends? (iv)Does inertia play any role for an object moving on a frictionless surface with uniform speed? Justify your answer. (v)Which of the following has more inertia- 10kg cotton bale or 5kg iron block?
Question 26.
(i)State Newon’s third law. (ii)Are the forces mentioned in the law balanced forces why? (iii) Will they always produce acceleration of equal magnitude? Why?
Question 27.
(i)What is law of conservation of momentum? Derive it? (ii)Which would require a greater force to accelerate a ½ kg mass at 5 m/s² or a 4 kg mass at 2 m/s²? Give reason.
Question 28.
Derive the velocity- position equation of motion (v²=u²+2aS) graphically (with the help of a velocity- time graph).

Summary

This Important Questions and answers on Motion for Class 9 physics with answers is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail.

Also Read

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• Notes
  • Class 9 motion notes
  • NCERT solutions for class 9 science chapter 8 intext and Exercise for Motion
• Assignments
  • Conceptual Questions and answers on Motion for Class 9
  • Numerical Questions and answers
  • Important Questions and answers on Motion for Class 9
  • Worksheet on Motion
  • Question Bank on Motion

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