Day 97: What If There’s More Than One Force?

IMG_20140225_144853723_HDR

College-Prep Physics: What if there’s more than one force? We used dueling fan carts and a motion detector to predict and test the outcomes of several scenarios. It turns out that …

2 carts, 1 fan on high (3F) ≈ 0.3 m/s/s

2 carts, 1 fan on medium (2F) ≈0.2 m/s/s

2 carts, 1 fan on low (1F) ≈0.1 m/s/s

So, what happens in the balanced cases?

IMG_20140225_130649034

Not terrible surprising. How about the unbalanced cases?

IMG_20140225_130642633

Then we returned to the PhET force and motion sim. We pushed the sleepy dog with 200 N (F1), turned friction on/off (F2), and looked at the resulting acceleratations:

IMG_20140225_130616950

Then I challenged the students to determine:

  • When there’s friction, how hard should we push so that we get the same acceleration as without friction?
  • When there’s no friction, how hard should we push so that we get the same acceleration as with friction?

Students made their predictions and we tested using the simulation. Now we can modify the equation we derived yesterday and change force to net force.

##UBFPM

Advertisements

About Frank Noschese

HS Physics Teacher constantly questioning my teaching.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: