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Perfectly elastic oblique collision is considered one the most difficult concept.
Perfectly Elastic Head on Collision, Head on inelastic collision, Perfectly inelastic collision, Collision Between Bullet and Vertically Suspended Block is considered one of the most asked concept.
34 Questions around this concept.
A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss (in Joule) during the collision is :
Two particles of masses m1, m2 move with initial velocities u1 and u2. On collision, one of the particles get excited to a higher level, after absorbing energy (E). If the final velocities of particles are v1 and v2 then we must have:
A large number (n) of identical beads, each of mass m and radius r are strung on a thin smooth rigid horizontal rod of length L (L>>r) and are at rest at random positions. The rod is mounted between two rigid supports (see figure). If one of the beads is now given a speed, the average force experienced by each support after a long time is (assume all collisions are elastic) :
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Two identical balls A and B having velocities of 0.5 m/s and -0.3 m/s respectively collide elastically in one dimension. The velocities of B and A after the collision respectively will be:
Two particles A and B of equal mass M are moving with the same speed v as shown in the figure. They collide completely inelastically and move as a single particle C. The angle θ that the path of C makes with the X-axis is given by :
The question contains Statement-1 and Statement-2. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement-1: Two particles moving in the same direction do not lose all their energy in a completely inelastic collision.
Statement-2: The principle of conservation of momentum holds true for all kinds of collisions.
A mass m moves with a velocity and collides inelastically with another identical mass .After collision the first mass moves with velocity in a direction perpendicular to the initial direction of motion.Find the speed of the 2nd mass after collision
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In Perfectly Elastic Collision,
Law of conservation of momentum and that of Kinetic Energy hold good.
…….(1)
…….(2)
From equation (1) and (2)
We get, …..(3)
Or, we can say Relative velocity of approach = Relative velocity of separation
And
So in Perfectly Elastic Collision
e = 1 ,
From equations (1),(2), (3)
We get
……(4)
Similarly, ...... (5)
Special cases of head on elastic collision
Equal mass in case of perfectly elastic collision
Then,
Or, Velocity mutually interchange
If massive projectile collides with a light target (i.e )
Since so we use
Putting in equation (4) and (5)
We get
If target particle is massive in case of elastic collision (i.e; )
Since
So, the lighter particle recoil with same speed and the massive target particle remain practically at rest.
i.e;
Let two bodies moving as shown in figure.
By law of conservation of momentum
Along x-axis-
….. (1)
Along y-axis-
…..(2)
By law of conservation of kinetic energy
….(3)
And In Perfectly Elastic Oblique Collision
Value of e=1
So along line of impact (here along in the direction of )
We apply e=1
And we get ….. (4)
So we solve these equations (1),(2),(3),(4) to get unknown.
Special condition
Then, from equation (1), (2) and (3)
We get,
i.e; after perfectly elastic oblique collision of two bodies of equal masses (if the second body is at rest), the scattering angle would be .
In Inelastic Collision Law of conservation of momentum hold good but kinetic energy is not conserved .
…… (1)
In inelastic collision (0 < e < 1)
….. (2)
From equations (1),(2)
We get,
……(3)
Similarly, ...... (4)
Special case
A sphere of mass m moving with velocity u hits inelastically with another stationary sphere of same mass.
As,
So, or, ....(5)
By conservation of momentum
As,
So ….(6)
From equation (5) and (6)
We get,
Loss in kinetic energy
Loss in K.E = Total initial kinetic energy – Total final kinetic energy
…. (7)
From equation (3) , (4) and (7)
We can write, Loss in kinetic energy in terms of e as
In Perfectly Inelastic Collision - Two bodies stick together after the collision ,so there will be a final common velocity (v)
When the colliding bodies are moving in the same direction
By the law of conservation of momentum
Loss in kinetic energy
When the colliding bodies are moving in the opposite direction
By the law of conservation of momentum
If v is positive then the combined body will move along the direction of motion of mass
If v is negative then the combined body will move in a direction opposite to the motion of mass
Loss in kinetic energy
A block of mass M suspended by vertical thread.
A bullet of mass m is fired horizontally with velocity u in the block.
Let after the collision bullet gets embedded in block.
And, the combined system raised upto height h where the string makes an angle with the vertical.
Common velocity of system just after the collision (V)
Here, system is (block + bullet)
.....(1)
Initial velocity of the bullet in terms of h
By the conservation of mechanical energy
Loss in kinetic energy
Loss of kinetic energy in perfectly inelastic collision when is given by
Value of angle
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