answer
the final velocity is half of train car B's initial velocity
explanation
the conservation of momentum states that the initial and final total momentum are equal
m1v1 + m2v2 for initial momentum
(m1 + m2)v3 for final momentum because both cars stick together so their masses are combined
m1v1 + m2v2 = (m1 + m2)v3
since the mass of both are the same, m1 = m2
m1v1 + m1v2 = (m1 + m1)v3
m1(v1 + v2) = 2m1v3
divide both sides by m1
v1 + v2 = 2v3
since train car A is initially at rest, v1 = 0
v2 = 2v3
v3 = v2 * 1/2
the final velocity is half of train car B's initial velocity
Answer:
16m/s
Explanation:



Therefore, the speed after 8 seconds is 16m/s
Answer:
The population size decreases.
Explanation:
If more of a species are dying than being born, the population size will decrease.
Answer:
The frictional force
6.446 N
The acceleration of the block a = 6.04 
Explanation:
Mass of the block = 3.9 kg
°
= 0.22
(a). The frictional force is given by


3.9 × 9.81 × 
29.3 N
Therefore the frictional force
0.22 × 29.3
6.446 N
(b). Block acceleration is given by

F = 30 N
= 6.446 N
= 30 - 6.446
= 23.554 N
The net force acting on the block is given by

23.554 = 3.9 × a
a = 6.04 
This is the acceleration of the block.