Question

A body 'A' of mass 1.5kg travelling along the positive X-axis with speed of 4.5m/s collides with another body 'B' of mass 3.2kg, which initially is at rest as a result of the collision, 'A' is deflected and moves in a speed of 2.1m/s in a direction which is at an angle of 30 degree below the X-axis. 'B' is set in motion at an angle Φ above the X-axis. calculate the velocity of 'B' after the collision.

Answer 1

We know that

m(A)u(A) = m(A)v(A) + m(B)v(B), since u(B) = 0 as B is at rest
calculate v(A) using:
Vx = Vcos∅Vx = 2.1cos(30)Vx = 1.82 m/s
1.5 x 4.5 = 1.5 x 1.82 + 3.2v(B)v(B) = 1.26 m/s
The deflection angle of B will be 30° above the positive x-axis, so:v(B) = Vcos∅V = 1.26 / cos(30)V = 1.45 m/s
the answer isthe velocity of B is 1.45 m/s