Tag: collisions

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Questions Related to collisions

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

In elastic collision, $A$ is conserved while in inelastic collision $B$ is conserved.
I.Momentum
II.Kinetic Energy
III.Potential Energy

  1. $A$ = I, II
    $B$ = I, III
  2. $A$ = I, III
    $B$ = I
  3. $A$ = III
    $B$ = II, III
  4. $A$ = II
    $B$ = I, III
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Collision can be elastic, which means they conserve  both K.E. and momentum. In inelastic collision, they only conserve momentum but not K.E. 
Multiple choice force exerted by collision collisions work, energy and power mechanics physics

In an elastic collision of two particles the following is conserved.

  1. Momentum of each particle

  2. Speed of each particle

  3. Kinetic energy of each particle

  4. Total kinetic energy of both the particles
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Total kinetic energy, i.e., kinetic energy of the system is conserved.

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

Line which is common normal for surfaces in contact during impact is known as

  1. Line of impact

  2. Line of collision

  3. Line of energy

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

Line which is common normal for surfaces  in contact during impact is known as line of impact. This is the line along which internal force of collision acts during impact.

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

How much force is exerted on a gunner by the machine gun, when the gunner fires machine gun, and $500$ bullets per minute are fired . The mass of bullet is $10g$ and it moves at $400\ m/s$ so as to avoid recoil.

  1. $\dfrac{100}{3}N$
  2. $200N$
  3. $2000N$
  4. $1000N$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Force = rate of change of momentum. Force = (n * m * v) / t, where n/t = 500 bullets/60 seconds. Force = (500/60) * 0.01 kg * 400 m/s = (50/6) * 4 = 200/3 N. Wait, the calculation is (500/60) * 0.01 * 400 = (50/6) * 4 = 200/3. Re-evaluating: 500 bullets/min = 500/60 bullets/sec = 25/3 bullets/sec. Force = (25/3) * 0.01 * 400 = (25/3) * 4 = 100/3 N.

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

A ball of  mass $0.2kg$ is thrown against the wall$,$ the ball strikes the wall normally with velocity of $30m/s$ sand rebounds with velocity of $20m/s.$ Calculate the impulse of the force exerted by the ball on the wall

  1. $2N$
  2. $-10N$
  3. $20N$
  4. $40N$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given $, u = 30 m/s$ $, v = 20 m/s$ 

$m =  0.2 kg$
impulse $-$ change in momentum of the body$,$
$= mv - mu = m (v - u )$
$= 0.2 ( -20 -30 ) = -10 N$
Hence,
option $(B)$ is correct answer.

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

If a cricket ball hits you, it will hurt much more than a tennis ball would when moving with the same velocity because:

  1. a cricket ball is bigger

  2. a cricket ball has more mass

  3. a cricket ball has less density

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

Impulse "Ft" is defined as change in momentum.

The ball with more momentum will hurt more. Here, cricket ball will hurt more as it has more momentum (mv) than tennis ball.
This is because cricket ball has more mass and same velocity as that of tennis ball.
So option B is correct.

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

Two solid rubber balls $A$ and $B$ having masses $200$ grams and $400$ grams are moving in opposite directions with velocity of $A$ equal to $0.3   {m}/{s}$. After collision the two balls come to rest, then the velocity of $B$ is

  1. $0.15 {m}/{s}$
  2. $1.5 {m}/{s}$
  3. $- 0.15 {m}/{s}$

  4. None
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Initial linear momentum of system $= {m} _{A} \bar { { V } _{ A } } + {m} _{B} \bar { { V } _{ B } }$
                                                      $ = 0.2 \times 0.3 + 0.4 \times {V} _{B}$
Finally both balls come to rest.
Finally linear momentum $= 0$
By the law of conservation of linear momentum.
$0.2 \times 0.3 + 0.4 \times {V} _{B} = 0$
${V} _{B} = -\dfrac{0.2 \times 0.3}{0.4} = -0.15  {m}/{s}$

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

A shell of mass $m$ moving with velocity $V$ suddenly breaks into $2$ pieces. The part having mass ${m}/{4}$ remains stationary. The velocity of the other shell will be:

  1. $V$
  2. $2V$
  3. ${3}/{4} V$
  4. ${4}/{3} V$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Mass of the one part which remains at rest is $\dfrac{m}{4}$.
Thus mass of other shell is $\dfrac{3m}{4}$.
Using conservation of linear momentum :  $P _{initial} = P _{final}$
$m V = \dfrac{m}{4} \times 0 + \dfrac{3m}{4} V _2$
Or  $m V =   \dfrac{3m}{4} V _2$
$\implies$ $V _2 = \dfrac{4V}{3}$
Multiple choice force exerted by collision collisions work, energy and power mechanics physics

Two bodies having same mass $40   kg$ are moving in opposite directions, one with a velocity of $10  {m}/{s}$ and the other with $7   {m}/{s}$. If they collide and move as one body, the velocity of the combination is

  1. $10 {m}/{s}$
  2. $7 {m}/{s}$
  3. $3 {m}/{s}$
  4. $1.5 {m}/{s}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

By the conservation of momentum
   $40 \times 10 + \left(40\right) \times \left(-7\right) = 80 \times V$
   $V = 1.5   {m}/{s}$