Tag: force and it's unit

Questions Related to force and it's unit

A lift coming down is just about to reach the ground floor. Taking the ground floor as origin and positive direction upwards for all quantities, which of the following is correct ($x$=displacement, $v$= velocity, $a$=acceleration):

physics along with motion what forces can do? force and it's unit force and its effects

  1. $x < o, v<0, a>0$

  2. $x > 0, v < 0, a < 0$

  3. $x > 0, v < 0, a> 0$

  4. $x > 0, v >0,a >0$

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Correct Option: A

A particle moves in a potential region given by $U = 8{x^2} - 4x + 400\,J.$ Its state of equilibrium will be$-$ 

physics along with motion what forces can do? force and it's unit force and its effects

  1. 8 m

  2. 10 m

  3. 12 m

  4. 0.25 m

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Correct Option: D
Explanation:

$U = 8x^2 - 4x + 400$
Differentiate with $dx$ we will get $F$
$F = 16x - 4$
At equilibrium $F = 0$
$0 = 16x - 4$
$x = 1/4 = 0.25 m$
It’s state of equilibrium will be at $x = 0.25 m$

Hence,
option $(D)$ is correct answer.

Which of Newton's three laws does the following example illustrate? If you have a hockey pick sliding along a table, it will eventually come to a stop.

physics along with motion what forces can do? force and it's unit force and its effects

  1. Newton's First Law

  2. Newton's Second Law

  3. Newton's Third Law

  4. All of the above

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Correct Option: A,B,C,D

A force produces transnational motion:

physics along with motion what forces can do? force and it's unit force and its effects

  1. when the body is free to move

  2. when the body is hindered to move

  3. when the body is rigidly fixed

  4. when none of the above are true

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Correct Option: A
Explanation:

For the application of translational motion the body must be free to move and after applying force, all the particles in that body move with same velocity.

When no force acts on a body , it must be _______.

physics along with motion what forces can do? force and it's unit force and its effects

  1. Moving

  2. At rest

  3. In uniform motion

  4. Either B or C

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Correct Option: D
Explanation:

Both in uniform motion and when the body is at rest the net force on the body is zero or the body is said to be in equilibrium.

If we apply the brakes to a moving car, it comes to rest. This shows that force can make a moving object go slower.

physics along with motion what forces can do? force and it's unit force and its effects

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient

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Correct Option: A
Explanation:

Answer is A.

Friction prevents objects from moving or slows them down. It also causes wear on surfaces as they rub against each other and generates heat. Thus energy is wasted in overcoming friction. Hence, the force of friction can slow down an object.
Hence, the statement is true.

Eqbal has to push a lighter box and Seema has to push a similar heavier box on the same floor. Who will have to apply a larger force ?

physics along with motion what forces can do? force and it's unit force and its effects

  1. Eqbal

  2. Seema

  3. Both apply same force

  4. cant say

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Correct Option: B
Explanation:

Force of friction arises because of interlocking of irregularities on the two surfaces in contact. When a heavy object is placed on the floor, the interlocking of irregularities on the surface of box and floor become strong. This is because the two surfaces in contact are pressed harder. Hence, more force is required to overcome the interlocking. Thus to push the heavier box, Seema has to apply a greater force than Eqbal.

State whether true or false.
If a body is moving with a constant speed along a straight line, then in order to change its direction of motion, an external force or its component has to act in a direction normal to the direction of motion.

physics along with motion what forces can do? force and it's unit force and its effects

  1. True

  2. False

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Correct Option: B
Explanation:

Here, body is moving with constant velocity. 

To change its direction of motion,  an external force must act in the direction opposite to the velocity, so given statement is false. 

In which of the following cases, the net force acting on the body is not zero?

physics along with motion what forces can do? force and it's unit force and its effects

  1. An object floating in mercury

  2. A ball freely falling from a certain height

  3. A cork floating on the surface of water.

  4. All of the above cases.

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Correct Option: B
Explanation:

In the case of falling freely under gravity.

  By newton second law
 $F _{net}=ma$
in this case $a=(-g)$
Hence there is net force in downward direction.
Rest are all balanced.

Two bodies of masses ${m} _{1}$ and ${m} _{2}$ are acted upon by a constant force $F$ for a time $t$. They start from rest and acquire kinetic energies ${E} _{1}$ and ${E} _{2}$ respectively. Then $\dfrac{{E} _{1}}{{E} _{2}}$ is

physics along with motion what forces can do? force and it's unit force and its effects

  1. $\dfrac{{m} _{1}}{{m} _{2}}$

  2. $\dfrac{{m} _{2}}{{m} _{1}}$

  3. $1$

  4. $\dfrac{\sqrt{{m} _{1}{m} _{2}}}{{m} _{1}+{m} _{2}}$

Show answer
Correct Option: B
Explanation:

Bodies of mass $m _1$ and $m _2$ acted on by force F (say) for time t. Acceleration in mass $m _1$= $\dfrac{F}{m _1}$
Acceleration in mass $m _2$= $\dfrac{F}{m _2}$
Velocity acquired during this time for mass $m _1$
$v _1=\dfrac{F}{m _1} t$
Velocity acquired during this time for mass $m _2$
$v _2=\dfrac{F}{m _2} t$

Ratio of kinetic energy acquired
$\dfrac{E _1}{E _2}=\dfrac{\dfrac{1}{2}m _1v _1^2}{\dfrac{1}{2}m _2v _2^2}$
$\dfrac{E _1}{E _2}=\dfrac{m _1\times (\dfrac{F}{m _1} t)^2}{m _2\times (\dfrac{F}{m _2} t)^2}$
$\dfrac{E _1}{E _2}=\dfrac{m _2}{m _1}$