Tag: force and newton's laws of motion

Questions Related to force and newton's laws of motion

Hair of shaving brush cling together when it is removed from water due to

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. Force of attraction between hair

  2. Surface tension

  3. Viscosity of water

  4. Charactersitic property of hair

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Correct Option: B
Explanation:

When the brush is taken out of water, the hairs cling together due to surface tension. This happens because the free surface of water tries to acquire a minimum surface area.

Hence, option B is correct.

Which of the following Newton's law(s) is/are not applicable in non-inertial reference frame. 

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. Newton's first law

  2. Newton's second law

  3. Newton's third law

  4. All of these

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Correct Option: A
Explanation:

Newton's law(s) is/are not applicable in non-inertial reference frame in newton's first law.

so the option is A.

Is force needed to keep a moving body in motion? Which one of the Newton's laws follow this ?

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. No, first law.

  2. Yes, third law.

  3. No, second law

  4. Yes, first law.

Show answer
Correct Option: A
Explanation:

No, force is not needed to keep a moving body in motion. This is according to Newton's first law of motion.

A ball moving on a table top eventually stops. What is the reason ?

momentum and newton's laws newton's first law of motion first law of motion force and newton's laws of motion physics

  1. due to gravity.

  2. due to friction between the ball and table

  3. due to other external force.

  4. none of these.

Show answer
Correct Option: B
Explanation:

Due to the force of friction between the ball and table top, it  opposes the motion of the ball. And, gradually its speed keeps on decreasing and the ball finally stops.

Which Newton's law is related to the Galileo's law of inertia ?

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. Second.

  2. First

  3. First and second

  4. Third

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Correct Option: B
Explanation:

 Galileo's Law of Inertia stated: "A body moving on a level surface will continue in the same direction at constant speed unless disturbed."

Object will remain at rest or in uniform motion in a straight line unless acted upon by an external force - which law is this ?

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. Newton's third law

  2. Newton's first law

  3. Newton's second law

  4. None of these

Show answer
Correct Option: B
Explanation:

Statement of Newton's first law of motion,

It states that a body will remain at rest or in state of motion unless an external force is applied to the object.
To have any changes in state of object , force is necessary.

What is the force on a body of mass $m$ when it is moving with a constant velocity ?

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. $mg$

  2. $0$

  3. $\dfrac{m}{g}$

  4. $g$

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Correct Option: B
Explanation:

When a body moves with constant velocity, its acceleration is zero ($a=0$).

So, force required, $F=m \times a=m \times 0 = 0$

An aeroplane of mass is moving uniformly at a constant height under the action of two forces (i) upward force (lift) and (ii) downward force (weight). What is the net force on the aeroplane.

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. Zero.

  2. mg

  3. only downward force

  4. only upward force

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Correct Option: A
Explanation:

If the net force is not zero the plane would be moving upward or downward. Since its height is constant the net force is 0

The acceleration produced in a body by a force of given magnitude depends on:

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. size of the body

  2. shape of the body

  3. mass of the body

  4. none of these

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Correct Option: C
Explanation:

Newton's second law of motion, $F=ma$, where $m$ is mass of an object which acquires acceleration $a$ when force $F$ is applied on it.
For a force of constant magnitude, $a\propto{\dfrac{1}{m}}$ i.e. acceleration is inversely proportional to mass.

State whether given statement is True or False.
An object moving on a frictionless horizontal surface should move with constant velocity

physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

  1. True

  2. False

Show answer
Correct Option: A
Explanation:
True,
Newtons law of motion states that a body moving with constant velocity will continue moving with same velocity if any external force is absent. In the given case above case surface is frictionless and any other external force is absemt so body will move with same constant velocity.