1. TODAY and TOMORROW 1) Video about RAMPS is important
2) Lab: for next class
3) Quiz next class: 4 questions on all kinds of force stuff

2. Discuss how to write/submit lab (See last class notes)
Part 2/3
Discuss how to write/submit lab (See last class notes)

3. What you will be submitting
For Each Part:
Overall
-A picture of the setup.
-What you did to find the goal (your process, equipment used)
-The graph of what you are supposed to find
-The actual result of the relationship
-An explanation on WHY the result happened (i.e. the physics on why the relationship is the way it is)
-On a paper, each part has its own section
-All group member names
-Each section is clearly labeled
-The analysis questions
-A lab name that will make me smile/laugh/chortle as I read them

4. Block is in contact with 1 thing. With friction, that makes 2 forces.
Plus 1 non-contact force.
But…it will accelerate down the ramp. Lets draw the forces

5. The idea
The friction and normal force are not in X or Y. But the block will also not accelerate in X or Y.
So we will create a NEW frame of reference to make the physics easier.
Downhill/Uphill is X, Perpendicular to ramp is Y
So the weight is now not in the new X or Y, need to find its X and Y components

7. 1) Lets draw in the parallel and perpendicular parts of the weight
2) The two angles are the same due to geometry
Weight perpendicular to ramp (Y)
3) Using Sin and Cos we can find the X and Y parts of the weight
MgCos (θ)
Ramp angle
Weight parallel to ramp (X)
Weight
MgSin (θ) θ

8. Normal Force
4) Draw the forces now on the block in X and Y
Friction if moving downhill
5) Depending on the way the block is moving, draw friction
Weight perpendicular to ramp (Y)
Friction if moving uphill
MgCos (θ)
Weight parallel to ramp (X)
MgSin (θ)

9. RAMP REVIEW
Instead of X and Y, we are going to rotate to a ‘New X’ and ‘New Y’:
‘New X’ : Down/Uphill
‘New Y’ : Perpendicular to the hill
Weight in X is the SIN of the weight.
Weight in Y (perpendicular to ramp) is the COS of the weight

10. Lets create Net Force Equations and solve for the acceleration!
Moving downhill:

11. Lets create Net Force Equations and solve for the acceleration!
Moving Downhill

12. Lets create Net Force Equations and solve for the acceleration!
Moving uphill:

13. Lets create Net Force Equations and solve for the acceleration!
Moving uphill: