Forces and Laws of Motion Test

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Forces and Laws of Motion Test - 47

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Weekly Quiz Competition

Question 1
1 / -0

X and Y are two objects with masses $$100\ kg$$ and $$75\ kg$$ respectively, then :

A
Both will have the same inertia

B
Y will have more inertia

C
X will have more inertia

D
Can not be compared

Solution

The object having more mass has more inertia and vice-versa. As the object X has more mass than Y, thus X has more inertia.
Question 2
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An $$80\;\text{kg}$$ person is parachuting and is experiencing a downward acceleration of $$2.8\;\text{m/s}^2$$. The mass of the parachute is $$5\;\text{kg}$$. The net force on the system (parachute+man) is (Take $$\text{g=9.8 m/s}^2$$):

A
$$238\;N$$

B
$$675\;N$$

C
$$456\;N$$

D
$$925\;N$$

Solution

The net downward acceleration is $$2.8 m/s^2$$
According to Newton second law
$$F = ma$$
$$m$$=$$80+5=85$$ $$kg$$
Hence $$F = 85 \times 2.8$$N = $$238 N$$
Question 3
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Mark the correct statement.

A
Acceleration produced in a body $$\propto$$ force applied on the body

B
Acceleration produced in a body $$\propto \dfrac {1}{\text {Mass of the body}}$$

C
Both

D
None

Solution

From Newton's second law of motion $$a = \dfrac{F}{m}$$
$$\implies$$ $$a \propto F$$ and $$a \propto \dfrac{1}{m}$$
Hence option C is correct.
Question 4
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A fish is swimming in the ocean. Which of the following represents the interaction between the fish and the water?

A
The force of the fish points back while the force of the water points forward

B
The force of the fish must be greater than the force of the water for the fish to move

C
The force of the fish must be less than the force of the water for the fish to move

D
The forces point in the same direction in liquid media such as the ocean

E
Newton's third law does not apply in water

Solution

The forces on the fish and water forms an action-reaction pair.
The force on the fish by water is in forward direction as a reaction to the force on water by fish in backward direction.
This force on fish makes it move in the forward direction.
Question 5
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Use Newton's 2nd law of motion, find out the third missing quantity if mass and force on a body is given?

A
Displacement

B
Velocity

C
Acceleration

D
Linear momentum

E
Kinetic energy

Solution

From Newton's second law, $$force$$ $$(F)$$ $$=$$ $$mass (m)$$ $$\times$$ $$ acceleration (a)$$
As mass and force is given so missing quantity will be acceleration.
Question 6
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At the Earth, a block of mass $$m$$ which rest on the frictionless table, let $$F$$ be the force required to produce acceleration $$a$$. Calculate the force at the Moon to produce same acceleration if $$g_{moon}$$ is one sixth of $$g_{earth}$$.

A
$$\dfrac{F}{12}$$

B
$$\dfrac{F}{6}$$

C
$$\dfrac{F}{3}$$

D
$$F$$

E
$$6F$$

Solution

The force required to accelerate the block by $$a$$:
$$F=ma$$ which is independent of the value of gravitational force acting on the block vertically downwards.
Question 7
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A batsman hits a cricket ball which then rolls on a level ground. After covering a short distance, the ball comes to rest. The ball slows a stop because

A
The batsman did not hit the ball hard enough

B
Velocity is proportional to the force exerted on the ball

C
There is a force on the ball opposing the motion

D
There is no unbalanced force on the ball, so the ball would want to come to rest

Solution

Hint:
According to Newton's laws of motion, force is required to change the velocity of an object. The force is the product of mass and acceleration.
Step 1: Explaining the change in the velocity of the ball.
$$\bullet$$According to Newton's first law of motion, if a body is in a rest position, then it will remain in rest unless an external force is applied to it.
$$\bullet$$Therefore a force must be applied against its direction of motion to the ball to stop it.

Therefore option (C) is the correct answer.
Question 8
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The rubber band is stretched by the weight of the mass suspended on it, but it is not moving. The action force that causes the rubber band to stretch comes from the earth. Identify the reaction force of the force pair?

A
The rubber band pulling on the mass

B
The rubber band pulling on the earth

C
The mass pulling on the rubber band

D
The mass pulling on the earth

E
The earth pulling on the rubber band

Solution

The rubber band is stretched by the weight of the mass suspended on it, but it is not moving. The action force that causes the rubber band to stretch comes from the earth. The weight of mass suspended is working downwards and the rubber band pulling on mass is working in an upward direction as a reaction force.
Question 9
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A block rests on the floor. Two forces act, one is downward gravitational force and second one is upward reaction force by the floor. These two forces:

A
have equal magnitudes and the same direction

B
have equal magnitudes but opposite directions

C
have unequal magnitudes and the same direction

D
have unequal magnitudes and opposite directions

E
None of these

Solution

The magnitude of the gravitational force = The magnitude of the reaction force (As the block has no motion in the vertical direction)
the gravitational force is acting downwards whereas the reaction force is acting upwards.
Question 10
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A 60 kg man pushes a 40 kg man with a force of 60 N. With what force does the 40 kg man push the other man?

A
40 N

B
0 N

C
60 N

D
20 N

Solution

According to Newton's third law both the man pushes each other with same force ie 60N.

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Re-Attempt Weekly Quiz Competition

Forces and Laws of Motion Test - 47

Result

Forces and Laws of Motion Test - 47

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SHARING IS CARING

Question 1

Both will have the same inertia

Y will have more inertia

X will have more inertia

Can not be compared

Solution

Question 2

$$238\;N$$

$$675\;N$$

$$456\;N$$

$$925\;N$$

Solution

Question 3

Acceleration produced in a body $$\propto$$ force applied on the body

Acceleration produced in a body $$\propto \dfrac {1}{\text {Mass of the body}}$$

Both

None

Solution

Question 4

The force of the fish points back while the force of the water points forward

The force of the fish must be greater than the force of the water for the fish to move

The force of the fish must be less than the force of the water for the fish to move

The forces point in the same direction in liquid media such as the ocean

Newton's third law does not apply in water

Solution

Question 5

Displacement

Velocity

Acceleration

Linear momentum

Kinetic energy

Solution

Question 6

$$\dfrac{F}{12}$$

$$\dfrac{F}{6}$$

$$\dfrac{F}{3}$$

$$F$$

$$6F$$

Solution

Question 7

The batsman did not hit the ball hard enough

Velocity is proportional to the force exerted on the ball

There is a force on the ball opposing the motion

There is no unbalanced force on the ball, so the ball would want to come to rest

Solution

Question 8

The rubber band pulling on the mass

The rubber band pulling on the earth

The mass pulling on the rubber band

The mass pulling on the earth

The earth pulling on the rubber band

Solution

Question 9

have equal magnitudes and the same direction

have equal magnitudes but opposite directions

have unequal magnitudes and the same direction

have unequal magnitudes and opposite directions

None of these

Solution

Question 10

40 N

0 N

60 N

20 N

Solution

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