Tag: momentum and newton's laws

Questions Related to momentum and newton's laws

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

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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

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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.

An object moving at constant velocity must:

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

  1. have a net force on it

  2. eventually stop due to gravity

  3. not have any force of gravity on it

  4. have zero net force on it

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Correct Option: D
Explanation:

The object moving with constant velocity must have zero acceleration i.e. $a _{net} = 0$. From Newton's IInd law the net external force must be zero in case of zero acceleration.

Net external force acting on the object  $F _{net} = ma _{net} = 0$
Hence answer D is correct.

Every body continues to be in its state of rest or of non-uniform motion in a straight line unless compelled by some external force to act otherwise. This is stated by:

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 1st law

  2. Newton's 2nd law

  3. Newton's 3rd law

  4. None of the above

Show answer
Correct Option: D
Explanation:

The premise of question is external force is zero and conclusion is  state of motion of body will be at rest or non uniform motion. However, the non uniform motion is only applicable in case of external force being applied to body, hence the statement is false.

So, given statement is stated by none of Newton's laws.

If no net force acts on an object, then the velocity of the object:

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

  1. remains same

  2. becomes zero

  3. increases

  4. decreases

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Correct Option: A
Explanation:

Newton's first law indicates that if no net force acts on an object, then the velocity of the object remains unchanged.

If there are many forces acting on an object, it must have a non-zero net (unbalanced) force acting on it.

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

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Correct Option: B
Explanation:

In case of many forces acting on the body, it can be in equilibrium,which implies zero external force. For example in case of ladder supported by a wall there are frictional and gravitational forces working at wall and floor, which balances each other so that ladder does not move. Hence the given statement is false.