Tag: force and newton's laws of motion

Questions Related to force and newton's laws of motion

Inertia is the property of a body which preserves its state of motion or uniform motion in a straight line. The following factors tell me about inertia.
I. Greater the mass of a body, greater is its inertia.
II. Greater the inertia of a body, the less will be the acceleration produced by a given force.
III. The law of inertia is the same as Newton's first law of motion. 
Which combination is true?

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

  1. I and III only

  2. I and II only

  3. I, II and III

  4. II and III only

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Correct Option: C

A block is moved from rest through a distance of 4m along a straight line path.The mass of the block is 5 kg,and the  force acting on it is 20 N.If the kinetic energy acquired by the block be 40J,at what angle to the path the force is acting:

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

  1. $30^o$

  2. $60^o$

  3. $45^o$

  4. none of the above

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Correct Option: B
Explanation:
From work Energy theorem 
$ \triangle w = \triangle KE $ 
$ F.S = K.E $
$ F.S cos\theta = KE  $
$ cos\theta = \frac{KE}{FS} $
$ cos\theta = 1/2 $
$ \theta = 60^{\circ} $ 

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

physics force and newton's laws of motion momentum (p) introduction to momentum linear momentum

  1. $(mv)^2$

  2. $mv^2$

  3. $1/2\ mv^2$

  4. $mv$

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Correct Option: D
Explanation:

Momentum of an object is defined as the product of its mass and the velocity with which the object is moving.

Let velocity of the object be  $v$ and its mass be  $m$
$\therefore \text{Momentum},\ P = mv$

A bullet of mass 40 g moving with a speed of $90 ms^{-1}$ enters a heavy wooden block and is stopped after a distance of 60 cm. The average resistance force exerted by the block on the bullet is

physics force and newton's laws of motion momentum (p) introduction to momentum linear momentum

  1. 180 N

  2. 220 N

  3. 270 N

  4. 320 N

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Correct Option: C

Force is directly proportional to

physics force and newton's laws of motion momentum (p) introduction to momentum linear momentum

  1. Rate of change in distance

  2. Rate of change in velocity

  3. Momentum

  4. Rate of change in momentum

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Correct Option: D
Explanation:

Second law of motion yields $F = \Delta p/\Delta t$

Which has a greater momentum, an elephant at rest or an ant in motion?

physics force and newton's laws of motion momentum (p) introduction to momentum linear momentum

  1. Elephant

  2. Ant

  3. Neither has momentum

  4. Same

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Correct Option: B
Explanation:

Momentum combines both mass and velocity. Ant has a greater momentum because of it is moving. Momentum of the elephant would be zero because it is at rest.

$SI$ units of momentum is _____ 

physics force and newton's laws of motion momentum (p) introduction to momentum linear momentum

  1. $kg\, m/s^2$

  2. $kg \,m/s$

  3. $g \,km/hr$

  4. $kg\, km/hr$

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Correct Option: B
Explanation:

$SI$ unit of momentum $= (SI\, \text{unit of}\, m).(SI\,\text{ unit of}\, v) = kg \,m/s$

The SI unit of linear momentum is $kg \ m/s^{-1}$.

physics force and newton's laws of motion momentum (p) introduction to momentum linear momentum

  1. True

  2. False

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Correct Option: A
Explanation:

Momentum = mv

Unit: kg * m/ s
So, given statement is true.

If the same force is applied on two bodies of different masses for the same time, then the change produced in the momentum of the two bodies is also same .

physics force and newton's laws of motion momentum (p) introduction to momentum linear momentum

  1. True

  2. False

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Correct Option: A
Explanation:

According to Newton's second law,

F = ma = m (v - u)/ t
Ft = mv - mu = Change in momentum
Now, for two bodies, if Ft is same, change in momentum is also same.
So, given statement is true.

Momentum is a measure of quantity of motion.

physics force and newton's laws of motion momentum (p) introduction to momentum linear momentum

  1. True

  2. False

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Correct Option: A
Explanation:

For motion there are two factors, How much is moving? and how fast is moving?

According to that force changes.
So mass and velocity both are important. Hence momentum(P = mv) is quantity of motion.