Question

please explain how you got your answers so I can understand

The following relationships may be helpful. A spaceship of mass 4m kg moves in deep space along the x axis with an initial velocity 20i m/s and explodes in to two pieces of mass m kg and 3m kg as shown in the figure at right. Immediately after the explosion, the piece of mass m travels with a velocity 14 j m/s.

Answer 1

Ans 1) C ( linear momentum is conseved until no external force is applied)

Ans 2) C ( linear momentum conservervation ( m V (initial) = m1 V1 + m2 V2  (final) ) V is velocity vector

Ans 3) D ( imagine the disc and try to move fingers of your right hand in the direction of arrow in the diagram, The direction of torque as well as angular acceleration is the direction in which your thumb points, Right hand rule)

Ans 4)C ( using = $v^{^{2}} = u^{_{2}} + 2 \alpha \theta , \theta = 2 \pi r , u =0$ )

Ans 5) A ( torque = I * alpha, alphs from previous question, and I ( moment of inertia) = m * r² (point mass at distance r )

Ans 6) D (torque = F x r; but here we are asked about the reaction at origin thus = - ( F x r))

Ans 7) B (Energy is conserved)

Ans 8) B ( Ring has highest moment of inertia, it gains the most amount of energy)