Can a Strong Man Push Two Freight Cars at Different Speeds?

[lynaa]

Homework Statement

The strong man will push the two initially stationary freight cars of equal mass apart before he himself drops straight to the ground. Is it possible for him to give either of the cards a greater speed than the other? Why or why not?

Homework Equations

None this is a theory question.

The Attempt at a Solution

It is not possible for the strongman to push either of the cars with a greater speed than the other because when the man pushes against one car, he is using the other car as a brace. So the force of the man pushing on one car would create a reaction force against the second car.

I am not really sure this is the right answer. I don't completely understand this concept about action and reaction forces yet.

 

[rude man]

So the force of the man pushing on one car would create a reaction force against the second car.

.

That part is right.

Is the "reaction" force on the second car equal in magnitude to the force on the first car?

 

[lynaa]

That part is right.

Is the "reaction" force on the second car equal in magnitude to the force on the first car?

I think it should be because of Newton's third law? Or do I not understand how his law works as well?

 

[rude man]

I think it should be because of Newton's third law? Or do I not understand how his law works as well?

Correct.
Now, if the same force magnitude is applied to objects of differing mass, would you expect them to move with the same magnitude of acceleration?

 

[HalfLostAndSearching]

Your understanding is correct. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. In this scenario, the strongman is applying a force on one car, but that force is also being exerted on the other car in the opposite direction. This means that the cars will move away from each other with equal speeds, as the force applied on each car is the same. Therefore, it is not possible for the strongman to give one car a greater speed than the other.