Phet Lab Simulation: Understanding Newton's Laws!

Go to the following link, select the "motion" activity, and play around with it.  How does adding more mass impact the acceleration of the the skateboard? What about adding more force? Do your observations line up with what you expect from Newton’s second law? Why or why not? 

For an extra challenge, try to use Newton's second law to determine the mass of the present, which has an unknown mass. 

https://phet.colorado.edu/sims/html/forces-and-motion-basics/latest/forces-and-motion-basics_all.html