Question

Consider a collision between two identical masses of 0.051 kg on a frictionless surface. Initially one of them is at rest and the other approaches with a velocity of 2.59 m/s.When they collide, they "stick" together and leave the collision as one combined object.

(a) Find the velocity of the combined system as it leaves the collision.


(b) Is the kinetic energy in this collision conserved?

Answer 1

here,

mass of each mass ,m = 0.051 kg

initial speed , u = 2.59 m/s

a)

let the velocity of the combined system as it leaves the collision be v

using conservation of momentum

m * u = ( m + m) * v

2.59 = 2 * v

solving for v

v = 1.3 m/s

the the velocity of the combined system as it leaves the collision is 1.3 m/s

b)

the initial kinetic energy ,KEi = 0.5 * m * u^2 = 0.5 * 0.051 * 2.59^2 = 0.17 J

the final kinetic energy ,KEf = 0.5 * 2 * m * v^2 = 0.5 * 2 * 0.051 * 1.3^2 = 0.085 J

as KEi is not equal to KEf

the kinetic energy in this collison is not conserved