Class: 9 Month: June Worksheet Number: 09/Sci/09/02
Subject: Science Chapter: 09–Force and laws of
motion
Name:
____________________________________________
Section A: Exposition
Each question carries 1 mark :
1.
Write
the SI unit of the following:
(i)
Momentum
(ii) Impulse
2.
Write the formula for Newton’s second
law of motion in terms of force F, mass m and acceleration a.
3.
State
Newton’s third law of motion.
4.
Name
a physical quantity which is the product of object’s mass and velocity.
5.
Which
law will you use to explain the following cases;
(i)
A
cricket player lowers his hand while catching a ball.
(ii)
It
is difficult to run on sand than on a hard surface.
(iii)
To
move a boat, a boat man has to row boat in opposite direction.
(iv)
It
is difficult to jump wearing skates.
6.
Name
a physical quantity which is the product of force and time interval.
7.
Write the formula for Newton’s second
law of motion in terms of force F, change in momentum m (v-u) and time
t.
8.
What
is S.I. unit of force?
9.
What
is the unit of force in terms of kilogram, metre and second?
10.
What
is the S.I. unit of action and reaction?
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Class: 9
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Worksheet Number: 09/Sci/09/02
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Subject: Science
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Chapter: 09–Force and laws of
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Each question
carries 2 marks :
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12.
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Define the following: (i) Momentum
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(ii) Impulse
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(iii) Force
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13.
State Newton’s second law of motion in
terms of the force F, time t and change in the momentum p2-p1
of the body.
Each
question carries 3 marks :
14.
Why
it hurts more when we hit a hard wall than a soft sponge?
15.
Why you may get hurt more if you jump on
a hard concrete floor than on a soft sandy surface from the same height?
16.
When you pull your arms back while
catching a fast moving cricket ball, the chances of hurting your hand are low.
Explain it on the basis of Newton’s law.
17.
Derive mathematical formulation for
Newton’s second law of motion in terms of force F, momentum p and
time t.
Section
B: Extended Exposition
Each question carries 2 marks :
18.
Represent following:
(a)
momentum versus velocity graph when mass is fixed.
(b)
momentum versus mass graph when velocity is constant.
19.
Using Newton’s second law of motion,
show that if there is no net force acts on a body; the body moves with uniform
velocity.
Each
question carries 3 marks :
20.
Akhtar, Kiran and Rahul were riding in a
motorcar that was moving with a high velocity on an expressway when an insect
hit the windshield and got stuck on the windscreen. Akhtar and Kiran started
pondering over the situation. Kiran suggested that the insect suffered a
greater change in momentum as compared to the change in momentum of the
motorcar (because the change in the velocity of the insect was much more than
that of the motorcar). Akhtar said that since the motorcar was moving with a
larger velocity, it exerted a larger force on the insect. And as a result the
insect died. Rahul while putting an entirely new explanation said that both the
motorcar and the insect experienced the same force and a change in the
momentum. Comment on these suggestions.
21.
Derive
the mathematical relation between momentum and kinetic energy of a body.
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Class: 9 Month: June
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Worksheet Number: 09/Sci/09/02
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Subject: Science
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Chapter: 09–Force and laws of
motion
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Section C:
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Interpretation
& Reasoning
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Each question carries 1 mark :
22.
A feather of mass 20 g is dropped from 2
m height. It fall with a constant velocity. If acceleration due to gravity is
10 m/s2, What is the net force
acting on it? Why?
Each
question carries 2 marks :
23.
A body of mass 2 kg is moving with a
velocity 10 m/s and a stone of mass 30 g is moving with a velocity 54 km/s.
Which will exert more impact on colliding/striking with an object and why?
24.
A sled on ice moves in the way described
in questions i – vii below. Friction is so small that it
can be ignored. A person wearing spiked shoes standing on the ice can apply a
force to the sled and push it along the ice. Choose one force (A - G)
which would keep the sled moving as described in each statement below.
i.
Which force would keep the sled
moving toward the right speeding at a constant acceleration?
ii.
Which force would keep the sled moving toward the
right at a constant velocity?
iii.
The sled is moving towards the
right. Which force would slow it at a constant acceleration?
iv.
Which force would keep the sled
moving towards the left and speeding up at constant acceleration?
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Class: 9 Month: June Worksheet Number: 09/Sci/09/02
Subject: Science Chapter: 09–Force and laws of
motion
v.
The sled was started from rest and
pushed until it reached a constant velocity towards right. Which force would
keep the sled moving at this velocity?
vi.
The sled is slowing down at a
constant acceleration and acceleration has right direction. Which force would
account for this motion?
vii.
The sled is moving toward the left.
Which force would slow it down at a constant acceleration?
E
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Class: 9 Month: June
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Worksheet Number: 09/Sci/09/02
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Subject: Science
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Chapter: 09–Force and laws of
motion
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Each question carries 3 marks :
29.
Two bodies are having momentum 3 kgm/s
and 7 kgm/s. if their speeds are 13 m/s and 15 m/s respectively, which one has
more mass?
30.
A body of mass 2 kg and a ball of mass
200 g having the same momentum. Which one has more speed?
31.
The velocity of a particle of mass 150 g
changes from 8 m/s to 12 m/s in 2 seconds. Assuming that a constant force acts
on it, find the magnitude of the force.
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Class: 9 Month: June
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Worksheet Number: 09/Sci/09/02
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Subject: Science
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Chapter: 09–Force and laws of
motion
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32.
Two balls A and B of masses ‘m’ and ‘2
m’ are in motion with velocities ‘2 V’ and ‘V’ respectively. Compare
(i)
their
momentum and
(ii)
the
force needed to stop them in the same time.
33.
Two bodies are having momentum 3 kgm/s
and 7 kgm/s. if their speeds are 13 m/s and 15 m/s respectively, which one has
more mass?
34.
A mechanic strikes a nail with a hammer
of mass 500g moving with a velocity of 20m/s. The hammer comes to rest in 0.02s
after striking the nail. Calculate the force exerted by the nail on the hammer.
35.
A force of 6 N produces an acceleration
of 2 m/s2 when it acts on a body
A and 3 m/s2 when it acts on
a body B. If the bodies A and B are joined together and a force of 5 N is
applied what will be the acceleration?
36.
A bullet of mass 5 g travelling at a
speed of 120 m/s penetrates deeply into a fixed target and is brought to rest
in 0.01s. Calculate (a) the distance of penetration in the target. (b) The
average retarding force exerted on the bullet.
37.
A mechanic strikes a nail with a hammer
of mass 500 g moving with a velocity of 20 m/s. The hammer comes to rest in
0.02s after striking the nail. Calculate the force exerted by the nail on the
hammer.
Each
question carries 5 marks :
38.
A 10 N force accelerates a body by 2 m/s2
and a 20 N force accelerates another body by 4 m/s2.
When both the masses are tied together, find the acceleration with:
(i)
Both 10 N and 20 N acting on them in the
same direction
(ii)
Both
10 N and 20 N is acting on them in the opposite direction.
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