Tag: forces

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Questions Related to forces

Multiple choice physics force concept of force and its unit force - push or pull forces

Force acting on a particle is 5 N. If the unit of length and time are doubled and unit of mass is halved then the numerical value of the force in the new unit will be ________ times the initial value.

  1. 1

  2. 2

  3. 3

  4. 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Force = $\displaystyle 5: : \frac{kg\times m}{sec^{2}}$
If unit of length and time are doubled and the unit of mass is halved
Then the unit of force will be $\displaystyle \left ( \frac{\frac{1}{2}\times 2}{(2)^{2}} \right )=\frac{1}{4}$ times
Hence the numerical value of the force will be 4 times (as numerical value $\displaystyle \propto\frac{1}{unit}$)

Multiple choice physics force concept of force and its unit force - push or pull forces

1 dyne is equal to

  1. 980 g wt

  2. $\displaystyle \frac{1}{980}$ g wt

  3. 980 kg wt

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

Dyne is unit of force specified in CGS system. 

So $ 1 dyne= 10^{-5} N $
And $ 1 N = \dfrac{1}{9.80} kg $
Now,
$ 1 dyne= \dfrac{1}{9.80} \times 10^{-5}  kg$


Changing kg into grams,
 $ 1 dyne = \dfrac{1}{9.80} \times 10^{-5}  \times 10^3 g $
So,
 $ 1 dyne= \dfrac{1}{980}g  \ wt $.

Multiple choice physics force concept of force and its unit force - push or pull forces

Which of the following sets of concurrent forces may be in equilibrium?

  1. $\displaystyle { F } _{ 1 }=3N,{ F } _{ 2 }=5N,{ F } _{ 3 }=1N$

  2. $\displaystyle { F } _{ 1 }=3N,{ F } _{ 2 }=5N,{ F } _{ 3 }=9N$

  3. $\displaystyle { F } _{ 1 }=3N,{ F } _{ 2 }=5N,{ F } _{ 3 }=6N$

  4. $\displaystyle { F } _{ 1 }=3N,{ F } _{ 2 }=5N,{ F } _{ 3 }=15N$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
"Forces are in equilibrium when vector sum of these three forces is zero and they form a triangle.
For a triangle, the sum of the two sides is always greater than the third side
Therefore, $F _1 = 3N; F _2 = 5N; F _3 = 6N$

$F _1 + F _2 > F _3$

$F _2 + F _3 > F _1$

$F _3 + F _1  > F _2$


Multiple choice physics force concept of force and its unit force - push or pull forces

In a game of tug of war, three girls of team $A$ pull the rope with forces of $100 N$, $120 N$ and $170 N$. In team $B$, the three members pull the rope with forces of $130 N$, $150 N$ and $155 N$. Who will win the tug of war? What is the resultant force?

  1. Team $A$, $55 N$

  2. Team $B$, $55 N$

  3. Team $A$, $45 N$

  4. Team $B$, $45 N$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Resultant force is nothing but the total force acting on a body including their directions. If the object is at rest or it moves with a same velocity, the resultant force should be zero. All forces are acting on same direction, resultant force should be the sum of all the forces.

In this case, the forces applied by team A are 100 N, 120 N and 170 N. The total force is 100 N+120 N+170 N = 390 N. The forces applied by tema B are 130 N, 150 N and 155 N. The total force is 130 N+150 N+155 N=435 N.
Now, both the total forces are in the opposite direction as the team are in the opposite direction. So, the resultant force is 435 - 390 = 45 N. 
Therefore, Team B will win in the game as they apply more force of 45 N.

Multiple choice physics force concept of force and its unit force - push or pull forces

Suppose a body that is acted on by only two forces, is accelerated. For this situation, mark the correct statement :
( Initial Velocity is non zero and in same direction as acceleration  ) 

  1. The body cannot move with constant speed

  2. The velocity can never be zero

  3. The sum of two forces cannot be zero

  4. The two forces must act in the same line
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

If the body is accelerating, then there is a net force which drives the body. Since the body is accelerating, velocity can not be zero or moving with a constant speed. 
It is not necessary that the two forces must act in the same line however they may act in the same line.

Multiple choice physics force concept of force and its unit force - push or pull forces

A force F is given by $F=at+bt^2$, where t is time. The dimensions of a and b are:

  1. $[MLT^{-3}]$and$ [MLT^{-4}]$

  2. $[MLT^{-4}]$and$ [MLT^{-3}]$

  3. $[MLT^{-1}]$and$ [MLT^{-2}]$

  4. $[MLT^{-2}]$and$ [MLT^{0}]$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given that $F=at+bt^2$ where $t$ is time.


For this equation to be dimensionally correct, the each term in the right hand side should have the dimensions of $F$

Dimensional formula of $F=[ MLT^{-2}]$

$\implies aT=[ MLT^{-2}]$
$\implies$ Dimension of $a$ is $[ MLT^{-3}]$

and
$\implies bT^2=[ MLT^{-2}]$
$\implies$ Dimension of $b$ is $[ MLT^{-4}]$

Hence, option $(A)$ is correct.

Multiple choice physics mechanics concept of force and its unit force - push or pull forces

What happens when two forces in the same direction, are applied on an object?

  1. Forces add up.

  2. Forces subtract.

  3. Resultant force is the division of forces.

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

When two forces are applied on a object in the same direction, forces added up and net force increases.

Multiple choice physics mechanics concept of force and its unit force - push or pull forces

When you and your friend push a table in opposite directions, it becomes difficult to move. This is because:

  1. the net force becomes the sum of  the two forces.

  2. the net force becomes the difference of the two forces.

  3. the table becomes heavier.

  4. the table becomes lighter.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When two forces are applied in opposite directions, the net force becomes the difference of the two. So, the net force becomes small and the table becomes difficult to move.

Multiple choice physics mechanics concept of force and its unit force - push or pull forces

In the game of tug-of-war, the team that pulls the rope harder wins the game. This is because:

  1. the rope moves in the direction of larger force.

  2. the rope moves in the direction of the smaller force.

  3. the rope does not move at all.

  4. the rope moves in the direction of product of the forces.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a game of tug-of-war, teams apply forces in terms of pulls on the rope. On the rope, two pulls act in opposite directions. The net force becomes the difference of the two forces (pulls) and the rope moves in the direction of the larger force (pull).