Collision of two rigid bodies - class-XI
Physics problems on collisions, coefficient of restitution, impulse, and momentum conservation in rigid bodies
Questions
A uniform rod AB of mass $3m$ and length $2l$ is lying at rest on a smooth horizontal table with a smooth vertical axis through the end $A$ . A particle of mass $2m$ moves with speed $2u$ across the table and strikes the rod at its mid point $C$. If the impact is perfectly elastic , then find the speed of the particle after impact if it strikes the rod normally
- $\dfrac{7u}{3}$
- $\dfrac{2u}{3}$
- $\dfrac{u}{3}$
- $\dfrac{4u}{3}$
A body falls from height 20 m.If coefficient of restitution 1/2. The time interval between starting point and second bounce is $\left( {g = 10;m{s^{ - 2}}} \right)$
- 1 s
- 2 s
- 3 s
- 4 s
A disc of mass $100g$ and radius $10cm$ has a projection on its circumference. The mass of projection is negligible. A $20g$ bit of putty moving tangential to the disc with a velocity of $5m{s}^{-1}$ strikes the projection and sticks to it. The angular velocity of disc is
- $14.29rad{s}^{-1}$
- $17.3rad{s}^{-1}$
- $12.4rad{s}^{-1}$
- $9.82rad{s}^{-1}$
Two spheres $A$ and $B$ of masses $m _1$ and $m _2$ respectively collide. $A$ is at rest initially and $B$ is moving with velocity $v$ along x-axis. After collision $B$ has a velocity $\cfrac{v}{2}$ in a direction perpendicular to the original direction. The mass $A$ moves after collision in the direction
- Same as that of $B$
- Opposite to that of $B$
- $\theta=\tan^{-1}{(1/2)}$ to the x-axis
- $\theta=\tan^{-1}{(-1/2)}$ to the x-axis
A rod of length on two metal pads of same height from a height $h$. The coefficients of restitution of the metal pads are ${e} _{1}$ and ${e} _{2}$ (${e} _{1}> {e} _{2}$). The angular velocity of the rod after it recoils is
- $\cfrac { { e } _{ 1 } }{ { e } _{ 2 } } l\sqrt { 2gh } $
- $\cfrac { { e } _{ 1 }-{ e } _{ 2 } }{ l } \sqrt { 2gh } $
- $\cfrac { { e } _{ 1 }+1 }{ { e } _{ 2 }+1 } \sqrt { 2gh } $
- $\cfrac { { e } _{ 1 }+1 }{ { e } _{ 2 }-1 } \sqrt { 2gh } $
In a collision between two solid spheres. velocity of separation along the line of impact (assume no external forces act on the system of two spheres during impact):
- Cannot be greater than velocity of approach
- Cannot be less than velocity of approach
- Cannot be equal to velocity of approach
- none of these
Two particles of mass $M _{A} $ and $M _{B} $ and there velocities are $V _{A} $ and $V _{B} $ respectively collides. After collision they inter changes their velocities then ratio of $\dfrac{M _{A}}{M _{B}}$ is:
- (a) $\dfrac{V _{A}}{V _{B}}$
- (b) $\dfrac{V _{B}}{V _{A}}$
- (c) $\dfrac{V _{A}+V _{B}}{V _{B}-V _{A}}$
- (d) 1
A plastic ball falls from a height of $4.9$ metre and rebounds several times from the floor. What is the coefficient of restitution during the impact with the floor if $1.3$ seconds pass from the first impact to the second one?
- $0.9$
- $0.1$
- $0.7$
- $0.8$
A body 'x' with a momentum 'p' collides with with another identical stationary body 'y' dimensionally. During the collision 'y' gives an impulse 'J' to the body 'x'. Then the coefficient of restitution is
- $\dfrac p{p-2J}$
- $\dfrac p{p-J}$
- $\dfrac p{p+2J}$
- $\dfrac p{p+J}$
A uniform rod AB of length $L$ and mass $M$ is lying on a smooth table. A small particle of mass $m$ strike the rod with a velocity $v _0$ at point C a distance x from the centre O. The particle comes to rest after collision. The value of $x$, so that point A of the rod remains stationary just after the collision, is:
- $L/3$
- $L/6$
- $L/4$
- $L/12$
a body of mass m falls from height h on ground. If e be the coefficient of restitution of collision betwwen the body and ground then the distance travelled by body before it comes to rest is
- $h\left\{ {\dfrac{{1\, + {e^2}}}{{1 - {e^2}}}} \right\}$
- $h\left\{ {\dfrac{{1\, - {e^2}}}{{1 + {e^2}}}} \right\}$
- ${\dfrac{{2eh}}{{1 + {e^2}}}}$
- ${\dfrac{{2eh}}{{1 - {e^2}}}}$
A solid spherical ball of radius R collides with a rough horizontal surface as shown in figure. At the time of collision its velocity is $v _{0}$ at an angle $\theta$ to the horizontal and angular velocity $\omega _{0}$ as shown. After collision, angular velocity of ball may
- decrease
- increase
- remains constant
- none of these
If a ball is dropped from rest, it bounces from the floor. The coefficient of restitution is $0.5$ and the speed just before the first bounce is $5\ m/sec$. The total time taken by the ball to come to rest is:
- $2\ sec$
- $1\ sec$
- $0.5\ sec$
- $0.25\ sec$
A solid sphere rolls without slipping on a rough horizontal floor, moving with a speed $v$. It makes an elastic collision with a smooth vertical wall. After impact,
- it will move with a speed $v$ initially.
- its motion will be rolling without slipping.
- its motion will be rolling with slipping initially and its rotational motion will stop momentarily at some instant.
- its motion will be rolling without slipping only after some time.
An athelete diving off a high spring board can perform a variety of physical moments in the air before entering the water below. Which one of the following parameters will remain constant during the fall? The athelete's:
- linear velocity
- linear momentum
- moment of inertia
- angular velocity
In an elastic collision, kinetic energy of the relative motion is converted into the ____ energies of two momentarily compressed bodies, and then is converted back into the _____ energy. Fill in the blanks.
- kinetic,kinetic
- elastic,kinetic
- elastic,elastic
- kinetic,elastic
State whether the given statement is True or False :
- True
- False
A ball of mass m moving with a constant velocity u strikes against a ball of same mass at rest. If e is the coefficient of restitution, then what will be the ratio of velocity of two balls after collision?
- $\dfrac{1-e}{1+e}$
- $\dfrac{e-1}{e+1}$
- $\dfrac{1+e}{1-e}$
- $\dfrac{e+1}{e-1}$
A sphere $A$ moving with speed $u$ and rotating with an angular velocity $\omega$ makes a head-on elastic collision with an identical stationary sphere $B$. There is no friction between the surfaces of $A$ and $B$. Choose the correct alternative(s). Discard gravity.
- $A$ will stop moving but continue to rotate with an angular velocity $\omega$
- $A$ will come to rest and stop rotating
- $B$ will move with speed $u$ without rotating
- $B$ will move with speed $u$ and rotate with an angular velocity $\omega$.
A 20 g ball is fired horizontally toward a 100 g ball that is hanging motionless from a 1.0-m-long string. The balls undergo a head-on, elastic collision, after which the 100 g ball swings out to a maximum angle of 50 degrees. Determine the initial speed of the 20 g ball.
- 8.4m/s
- 4.2m/s
- 2.1m/s
- 16.8m/s