Forces and Laws of Motion Test

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Forces and Laws of Motion Test - 8

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Weekly Quiz Competition

Question 1
1 / -0

“Forces always occur in pairs”. From which law can we conclude the above statement?

A
Newton’s first law

B
New tons second law

C
Newton’s law of gravitation

D
Newton’s third law

Solution

The force always occurs in pairs. According to third law of motion, there is equal and opposite reaction. So two force, action and reaction acts in pair on two different bodies always.
Question 2
1 / -0

Frictional force

A
always in the opposite director of motion

B
always in the direction of motion

C
always opposes motion of a body

D
always opposes relative motion between the surfaces of contact

Solution

Friction is a contact force always acting in the direction opposite to that of motion.
Question 3
1 / -0

‘Any two forces which are equal and opposite form an action and reaction pair’ The above statement is

A
true

B
false

C
partially true

D
partially false

Solution

The two forces acting on same body, which are in equal and opposite direction form action and reaction pair. This is the newton’s thirds law of motion.
Question 4
1 / -0

Find the incorrect statement about Newton’s law of action and reaction. Action and reaction

A
act simultaneously

B
are different in direction

C
act on same bodies

D
are equal in magnitude

Solution

Newton’s third law of motion explains action and reaction. Action and reaction acts simultaneously, are equal in magnitude. They act in different direction and acts on different bodies.
Question 5
1 / -0

Which is incorrect statement about action and reaction referred to Newton’s third law of motion?
A They are not equal
B They are opposite
C They act on same object
D They act simultaneously

A
(a) and (c)

B
(b) and (c)

C
(a), (b) and (c)

D
All of these

Solution

Action and reaction are equal and opposite and act on two different bodies simultaneously.
Question 6
1 / -0

Which of the following is not used to reduce friction

A
using oil between contact surfaces

B
using grease between contact surfaces

C
making scratches on the contact surfaces

D
using ball bearing

Solution

To reduce the friction, oiling between contact surfaces can be done, besides we can use ball bearing or grease between contact surfaces. Making scratches between contact surfaces will make the surface rough and so, will increase the friction.
Question 7
1 / -0

What is the momentum of an object of mass 1/2m, moving with a velocity 2v?

A
mv

B
mv²

C
(mv)²

D
1/2mv²

Solution

Momentum of a body is equal to product of mass and velocity. Momentum =1/2m × 2v = mv
Question 8
1 / -0

“Internal forces are forces which bodies exert on each other when the bodies are part of the system” is

A
true

B
false

C
partially false

D
partially true

Solution

Internal forces are those forces which are exerted on each other when the bodies are part of the system. The forces acting between the atoms of molecules that keep them together are example of internal force.
Question 9
1 / -0

According to the law of conservation of momentum

A
m₁u₁ − m₂u₂ = m₁v₁− m₂v₂

B
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

C
m₁u₁ + m₁u₁ = m₂v₂ + m₂v₂

D
None of the above

Solution

Law of conservation of momentum states that total momentum before collision is equal to total momentum after collision if no external force acts on it.
Question 10
1 / -0

A bullet of mass 10g is fired from a rifle. The bullet tales 0.003 second to move through its barrel and leaves it with a velocity of 300m|s. What is the force exerted on the bullet by the rifle?

A
1000N

B
400N

C
250N

D
200N

Solution

Mass of bullet = 10 g = 10/1000 kg.
initial velocity (u) = 0 and final velocity (v)= 300 m/s.
time (t)= 0.003 s
F= (mv-mu)/t
=(0.01x300 - 0.01x0)/0.003
=( 3-0)/0.003
= 3/0.003

=1000N

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Re-Attempt Weekly Quiz Competition

Forces and Laws of Motion Test - 8

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Forces and Laws of Motion Test - 8

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Question 1

Newton’s first law

New tons second law

Newton’s law of gravitation

Newton’s third law

Solution

Question 2

always in the opposite director of motion

always in the direction of motion

always opposes motion of a body

always opposes relative motion between the surfaces of contact

Solution

Question 3

true

false

partially true

partially false

Solution

Question 4

act simultaneously

are different in direction

act on same bodies

are equal in magnitude

Solution

Question 5

(a) and (c)

(b) and (c)

(a), (b) and (c)

All of these

Solution

Question 6

using oil between contact surfaces

using grease between contact surfaces

making scratches on the contact surfaces

using ball bearing

Solution

Question 7

mv

mv2

(mv)2

1/2mv2

Solution

Question 8

true

false

partially false

partially true

Solution

Question 9

m1u1 − m2u2 = m1v1 − m2v2

m1u1 + m2u2 = m1v1 + m2v2

m1u1 + m1u1 = m2v2 + m2v2

None of the above

Solution

Question 10

1000N

400N

250N

200N

Solution

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mv²

(mv)²

1/2mv²

m₁u₁ − m₂u₂ = m₁v₁− m₂v₂

m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

m₁u₁ + m₁u₁ = m₂v₂ + m₂v₂