Multiple Objects Getting Pushed or Pulled

How To Sove Force Problems With Multiple Objects Getting Pushed or Pulled

This video gives you an overview of the process for the type of problem where multiple objects are involved. The key to the process is that you'll need to do a free body diagram of each mass separately. Be sure to include the forces between the objects (F12, F23, etc.)!

Two Boxes Pushed Across Floor (no friction)

This video explains how to solve the most basic of the multi-object force problems: where a force is pushing two boxes across the floor without friction.

Two Objects Pushed Across Floor (with friction)

This video handles an example very similar to the previous video, except this time there is friction. That may seem like a small change, but it means quite a bit more math to keep track of, and it adds yet another arrow to each of your free body diagrams!

Find Contact Force Between Two Boxes Being Pushed Across Floor (no friction)

Rather than finding the acceleration of the two objects like we did in the previous examples, in this example we'll find the contact force between the two objects.

Two Objects Being Pulled Across Floor (with friction)

In this example, we mix things up a bit by having the two objects being pulled rather than pushed, and we're also given the force between the two objects and asked instead for the force pulling them.

Find Tension Between Train Cars

In this multi-object F=ma example we up the level of difficulty by adding a third object to the mix.

Three Objects Getting Pushed From One End (with friction)

In this penultimate multi-object force problem, we have three (count 'em, three!) boxes getting pushed, WITH FRICTION! That is going to be one big steaming pile of algebra, my friends: three equations, three unknowns, and enough substitution to power a city block.

Two Boxes Stacked-Bottom Getting Pushed-Find Friction Coefficient

This video may not seem like it's that bad, since we're back to doing only two objects, but I put it at the end of the chapter for a reason: it's a confusing doozy! If you don't believe me, try working it yourself first, and see if you manage to account for every force that needs to go in the free body diagram of the bottom box (hint: there should be 6).