Question

A block having mass m travels along a horizontal frictionless surface with speed vx. What impulse must be delivered to the mass to reverse its direction and continue to travel with a speed of vx?

A) -mvxB) -2mvxC) 0D) 2mvxE) mvxF) none of the aboveG) cannot be determined

Answer 1

Answer:B

Step-by-step explanation:

Given

mass of block is
`m`

Initial speed
`u=v_x`

final speed is reverse of initial with same magnitude
`v=-v_x`

Initial momentum
`P_i=mv_x`

Final momentum
`P_f=-mv_x`

change in momentum
`\Delta P=P_f-P_i`

Impulse
`J=\Delta P`

`J=-mv_x-mv_x`

`J=-2mv_x`