Answer:
26.4 m/s
Step-by-step explanation:
In the case of 2D inelastic collision the algebraic approach gets very complicated so it is better to use
Geometrical (vector) approach
In elastic inelastic collision the kinetic energy of the system decreases but the momentum is conserved
This means that the (vector) sum of the final velocities must be equal to the total initial velocity (i.e. it is equal to the initial velocity of the incoming particle).This means that the vector diagram is a right angled triangle, where the truck moving east and north can be shown as base and perpendicular respectively And the hypotenuse is the final velocity of system after collision.
Velocity of truck moving in North (h) = 16m/s
Velocity of the truck moving in East (b) = 21m/s
By Applying the Pythagoras theorem,
the final velocity of the system after collision (h) = √[b^2+h^2]
= √[21^2 + 16^2]
= √[441+256]
= √697
= 26.4m/s