Tag: mechanics

Quizzes (24) Questions (118)

Questions Related to mechanics

Multiple choice force exerted by collision collisions work, energy and power mechanics physics

Two equal masses ${m} _{1}$ and ${m} _{2}$ moving along the same straight line with velocities $+3  {m}/{s}$ and $-5  {m}/{s}$ respectively collide elastically. Their velocities after the collision will be respectively :

  1. $+4 {m}/{s}$ for both
  2. $-3 {m}/{s}$ and $+5 {m}/{s}$
  3. $-4 {m}/{s}$ and $+4 {m}/{s}$
  4. $-5 {m}/{s}$ and $+3 {m}/{s}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As ${m} _{1} = {m} _{2}$, therefore after elastic collision velocities of masses gets interchanged.

Multiple choice force exerted by collision collisions work, energy and power mechanics physics

A machine gun of mass 5 kg fires 30 bullets, each of mass 50 g, per minute at a speed of $400\,m\,{s^{ - 1}}$. What force must be exerted to keep the machine gun in position?

  1. $30N$
  2. $10N$
  3. $27N$
  4. $33N$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mass of the gun $=5kg$

Mass of bullets $=50g$
speed at which the bullet is fired$=400m/s$
Therefore$,$ force required to keep the machine gun in position $=\frac{{ch\arg e\,in\,momentum\,of\,bullets}}{{time\,taken}}$
$=\frac{{\left( {50 \times {{10}^{ - 3}} \times 30} \right) \times 400}}{{60}} = 10\,N$
Hence,
option $(B)$ is correct answer.

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).

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

When you and your friend pushes heavy table in the same direction, it becomes easier to move. This is because:

  1. the net force is the sum of forces.

  2. the net force is the difference of forces.

  3. the table becomes lighter.

  4. friction reduces.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When you and your friend pushes heavy table in the same direction, the force applied by you and your friend get added. So, applied forces sum up to get a larger force. Hence the table moves easily.

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

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

  1. Net force is the addition of forces.

  2. Net force is the subtraction of forces.

  3. Net force is the division of forces.

  4. Net force is the multiplication of forces.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When two forces are applied in the opposition direction on an object, the net force will be the difference between the two forces.

Multiple choice collisions in one dimension collisions work, energy and power mechanics physics

A particle of mass $1\ g$ moving with a velocity $\vec {v _{1}} = 3\hat {i} - 2\hat {j} ms^{-1}$ experiences a perfectly in elastic collision with another particle of mass $2\ g$ and velocity $\vec {v _{2}} = 4\hat {j} - 6\hat {k} ms^{-1}$. The velocity of the particle is:

  1. $2.3\ ms^{-1}$
  2. $4.6\ ms^{-1}$
  3. $9.2\ ms^{-1}$
  4. $6\ ms^{-1}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

From conservation of momentum
$m _{1}\vec {v _{1}} + m _{2}\vec {v _{2}} = (m _{1} + m _{2})\vec {v}$


$1\times (3\hat {i} - 2\hat {j}) + 2\times (4\hat {j} - 6\hat {k}) = (1 + 2)\vec {v}$

$\Rightarrow 3\hat {i} + 6\hat {j} - 12\hat {k} = 3\vec {v} $

$\Rightarrow \vec {v} = \hat {i} + 2\hat {j} - 4\hat {k}$


$v = |\vec {v}| = \sqrt {1 + 4 + 16} = 4.6\ ms^{-1}$.
Multiple choice collisions in one dimension collisions work, energy and power mechanics physics

A ball P moving with a speed of $v \ ms^{-1}$ collides directly with another identical ball Q moving with a speed $10\ ms^{-1}$ in the opposite direction. P comes to rest after the collision. If the coefficient of restitution is 0.6, the value of $v$ is:

  1. $30\ ms^{-1}$
  2. $40\ ms^{-1}$
  3. $50\ ms^{-1}$
  4. $60\ ms^{-1}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation


As momentum is conserved, we can say,

$m(v-10)=mv _2$

$v _2=(v-10)$

$e=\dfrac{v _2-v _1}{u _1+u _2}=\dfrac{(v-10)-0}{(v+10)}$

$0.6=\dfrac{v-10}{v+10}$

$0.6v+6=v-10$

$0.4v=16$ 

$v=40\ ms^{-1}$