Help very much needed!

Question

In an isolated system, Bicyclist 1 and Bicyclist 2, each with a mass of 80 kg, collide. Bicyclist 1 was moving to the right at 8 m/s, while Bicyclist 2 was moving to the left at 2 m/s. What is the magnitude of their combined momentum before the crash?

A. 480 kg-m/s
B. 640 kg-m/s
C. 80 kg-m/s
D. 160 kg-m/s

Answer 1

Help very much needed!
In an isolated system, Bicyclist 1 and Bicyclist 2, each with a mass of 80 kg, collide. Bicyclist 1 was moving to the right at 8 m/s, while Bicyclist 2 was moving to the left at 2 m/s. What is the magnitude of their combined momentum before the crash?

 

let V1=+8m/s

     V2=-2m/s

       m=80kg

(momentums (velocities as well) have opposite signs - as if moving to right or left)

 

Combined momentum before the crash, or, net momentum of the (isolated) system would be:

 

P=mV1+mV2=80*(8-2)kg*m/s=+480 kg*m/s (directed to right)

which is choice A