A freight train initially moving at +10m/s decelerates at a rate of -0.1m/s^2. How far does it move in 30 seconds?

255 [m].

Explanation:

1) the formula is (d - requred distance, V₀ - initial velocity, t - elapsed time, a - deceleration):

2) according to the formula above the required distance is:

d=10*30-0.5*0.1*900=300-45=255 [m].

Apply second equation of kinematics

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.