Tag: newton's first law of motion

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

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

  1. Newton's third law

  2. Newton's first law

  3. Newton's second law

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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.

  1. Zero.

  2. mg

  3. only downward force

  4. only upward force
Reveal answer Fill a bubble to check yourself
A Correct answer
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

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

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

  1. size of the body

  2. shape of the body

  3. mass of the body

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

An object moving at constant velocity must:

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

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:

  1. Newton's 1st law

  2. Newton's 2nd law

  3. Newton's 3rd law

  4. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
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.