Why Did This Tug-Of-War Strategy Work? 👁 

So at this point, we've learned a bit about some important vocabulary we can use to speak more specifically about the motion of objects: distance and displacement, speed and velocity, acceleration, and forces. We've seen how Newton's first law (

an object at rest will stay at rest and an object in motion will stay in motion unless acted on by an unbalanced force

) applies to situations like standing on a stopping bus, letting go of a moving skateboard, and getting tackled without good protective gear.

We've also seen how the second law of motion applies. The force that we apply on an object is directly proportional to how quickly it accelerates 

(also items with very little mass accelerate more given the same force than items with lots of mass). 

We've covered a lot already but there's probably a lot of things that don't make perfect sense yet — questions still unanswered.

Based on what you know already, do your best to answer this question with a detailed explanation that really gets into the physics based on the video. 

So an unbalanced force is when one side wins out the tug of war. It is a push or a pull that creates a net force in one direction.

Demo: Pulling or pushing from different sides on a swivel chair.

. Play with the simulation and run some experiments. (sum of forces is the same as the net force)

Answer the following based on the simulation:

(1) What happens when you have balanced amounts of force applied in opposite directions on an object? What is the net force in this situation?

(2) Gravity is also a force acting on the cart of candy even though it isn't shown in the diagram. But the cart isn't falling through the ground. What does that tell you about the upward force on the cart?

(3) How can you explain what happens in the simulation using 

. Play with the simulation and run some experiments.

(1) We know that objects with balanced forces on them keep moving at the same rate or stay at rest. When you push a skateboard why does it eventually come to a stop? What is the unbalanced force acting on a rolling skateboard?

(2) What will move further given the same force — a skateboard or a golf cart? Why?

(3) If there is an acceleration there is an unbalanced force behind it.

Draw the free body diagram for the head in 

 and explain why the head is knocked back by the paint can using the concept of balanced and unbalanced forces.

Get feedback on your free body diagram from a classmate.

A. Draw a sketch of what is happening in a notebook.

B. Transform into a free body diagram (remember to pay attention to lengths of arrows).

(1) A chandelier hangs at rest from a ceiling by a chain. Consider the forces acting on the chandelier.

(2) A baby is laying at rest on a bed. Consider only the forces acting on the baby. 

(3) A ball is shot vertically into the air with a toy gun. Consider the forces acting on the ball while it is rising in the air.

(4) A skydiver (who hasn't opened her parachute yet) falls at terminal velocity (constant speed). Consider the forces acting on the skydiver.

(5) A book rests on top of a table. Consider only the forces acting upon the book.

The Traveling Stones Of Death Valley 🧭 

In Death Valley, there are massive stones that seemingly move across the desert and leave paths behind them. How are these rocks traveling through the desert?

Mystery of Death Valley's Moving Stones Solved

 write an explanation of how and why the sailing stones move across the desert. 

Explain using specific evidence from the explore activities and draw a free body diagram below to show the forces acting on the stones. Your free body diagram model and explanation are thorough and accurate and demonstrate understanding of how net forces combine forces in different directions and how unbalanced forces affect the acceleration of objects.

Learn how free body diagrams can be used to model unbalanced forces on an object.

How Do Traveling Stones Move Through The Desert?