Two golf carts are driving towards each other. The first has a mass of 390 kg and is driving east at 20 m/s. The second has a mass of 500 kg and is driving west at 8 m/s. When the two collide their bumpers lock and are stuck together, what is the final speed of the connected golf carts? ( Note: In this problem consider east to be a positive direction and west to be a negative direction.)
Initial momentum
390*20 - 500*8 = 3800 , x direction
Final momentum = (390 + 500)v
= 890 v , x direction
But we all know from the first law deduced by Isaac Newton that since there are no external forces on this system in the x direction there will be no change in x momentum.
therefore:
890 v = 3800
v = 4.27 m/s , x direction (East)