First, we must recall that distance is the total length traveled by an object in which the direction of the motion does not matter. Meanwhile, displacement is the distance of the object from its starting point which means the directions matters for displacement.
Now, speed is distance over time while velocity is displacement over time. Since we're talking about the same object's motion, the total time traveled is (120 + 90) = 210 seconds.
Now, the total distance traveled by the object is (400 + 250) = 650 m. Meanwhile the total displacement traveled by the object is 400 m, East + 250 m, West = 150 m, East.
Now, to find the speed and velocity, we just divide the values of distance and displacement, respectively, over time. Thus, we have
speed = 650 m / 210s ≈ 3.095 m/s velocity = 150 m, East /210 s ≈ 0.714 m/s, East
Now, rounding the values up to 2 significant digits, we have
1. The balls move to the opposite direction but the same speed. This represents Newton's third law of motion. 2. The total momentum before and after the collision stays constant or is conserved. 3. If the masses were the same, the velocities of both balls after the collision would exchange. 4 and 5. Use momentum balance to solve for the final velocities.
