Answer:
The correct answer is option a.
Explanation:
Conservation of momentum :

Where :
= masses of object collided
= initial velocity before collision
= final velocity after collision
We have :
Two equal-mass carts roll towards each other.

Initial velocity of 
Initial velocity of
(opposite direction)
Final velocity of
(same direction )
Final velocity of
(same direction)


v = 0.5 m/s
rg135
The speed of the carts after their collision is 0.5 m/s.
Answer:
88.89kg
Explanation:
The formula for mass is m=F/a. If we plug in the values, we get m=400N/4.5m/s^2. The mass is 88.89kg. We know that the unit is in kg because one newton (N) is 1kg*m/s^2. The m/s^2 is cancelled out by the acceleration, and we are left with kg.