1. Pull the Cart you lazy Donkey!
Shrek and Donkey in
Pull the Cart you lazy Donkey!

2. If I pull on you and you pull on me with the same force can we move?

3. Donkey
Yeah Shrek
the horse ran off and we need you to pull the cart

4. That thing looks heavy

5. Yeah, but can you do it?

6. I’ve been studying physics and..
Ya, what? What do you know about Physics?

7. Shows what you know, I am edumacated, and Newton’s 3rd law says that if I apply a force on the carriage, the carriage will apply an equal and opposite force on me. The forces will cancel out and we won’t move.

8. Lazy, silly Donkey, that is not how Newton’s Third Law works!

9. If Donkey pulls on the cart will the cart pull back on him?

10. Is donkey right that the forces will cancel each other out?

11. Let’s look at the forces on Donkey
As long as the force of the ground pushing Donkey is greater than the force of the carriage pulling back, donkey will move.
Force of the ground pushing Donkey Forward
Force of the carriage pulling back on Donkey

12. Let’s look at the forces on the Carriage
As long as the force of Donkey is greater than the force of friction, the carriage will move.
Force of the Donkey pulling forward
Force of the friction pushing back on Carriage

13. Donkey will push on the ground and the ground will push back, allowing him to move the cart
The Forces Don’t cancel each other out because the are on different objects. one on the cart and one on Donkey

14. Ha Ha, Physics triumphs!