Explanation:
Average speed = distance / time
v_avg = 47 km / 1.72 hr
v_avg = 27.3 km/hr
Given:
Mass of the rail road car, m = 2 kg
velocity of the three cars coupled system, v' = 1.20 m/s
velocity of first car,
= 3 m/s
Solution:
a) Momentum of a body of mass 'm' and velocity 'v' is given by:
p = mv
Now for the coupled system according to law of conservation of momentum, total momentum of a system before and after collision remain conserved:
(1)
where,
= velocity of the first car
= velocity of the 2 coupled cars after collision
Now, from eqn (1)


v' = 1.80 m/s
Therefore, the velocity of the combined car system after collision is 1.80 m/s
It is gonna be C 0.37 and 19.1
Assuming that the box is moving when it is being pulled, Work is done on the box.
So work is the Force times the distance
W=Fd
But what is work actually ? When something moves due to force over some change in distance, it have energy.
But where does this energy come from ? Does it magically appear ? The energy comes from the applied force onto the box.
So the energy have been transferred. And it’s like that throughout the universe
Now to save time, I’ll just tell you the answer: kinetic energy
:)