Three identical train cars, coupled together are rolling east at 2.0 m/s. A fourth car traveling east at 4.0 m/s catches up with the three and couples to make a fourcar train. A moment later the train cars hit a fifth car that was at rest on the tracks, and it couples to make a five car train. What is the speed of the five car train?

The value is  

Explanation:

From the question we are told that

   The velocity of the each of the three cars is

    The velocity of the fourth car is  

    The initial velocity of the fifth car

Generally from the law of momentum conservation we have that

Given that the cars are identical then their mass will be the same

i.e

=>  

=>  

= >  

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards

im srry but ur wrong the answer is d a smooth rock, some red dirt, and an empty bird's nest.