Forces and Friction s1

Forces and Friction

Purpose: To determine the friction between two surfaces and then find the acceleration and forces associated with various systems.

Procedure:

1) Find m by setting up the ramp on the horizontal and adding enough hanging mass to get the block to move at a constant velocity; SF = 0

hanging

mass (Fh)

2) Add mass to the block (black rectangular blocks) and see how much hanging mass is needed to move the block at vc.

hanging

mass

3) Remove the mass and verify m by placing the ramp at the inverse tangent of m and seeing if the block slides down at vc When the block slides down at a constant velocity then Ff = -Fp (∑F = 0). And in the equation “m = Ff / Fn”, Ff can be replaced with Fp (Fp = -Ff), so the equation becomes “m = Fp / FN”, where Fp = sinq Fw and FN = cosq Fw. Note that the Fw’s cancel and m = sinq/ cosq = tanq. Therefore, when the block slides down the ramp at vc then “m = tanq”

4) Adjust the ramp to a higher angle determine the angle. Using 2nd Law and parallel and perpendicular forces calculate the forces acting and acceleration the block (without additional mass). Verify that calculation by placing a photogate half way down the ramp and finding the acceleration of the block

Show all data and calculations.

1) mass hanging; mh = ______g; ______kg; Fx = ______N, Ff = ______N

mass of block; mb = ______g; ______kg; Fw = ______N; FN = ______N

Show work:

m =

2) mass hanging; mh = ______g; ______kg; Fx= ______N, Ff = ______N

mass of block; mb = ______g; ______kg; Fw = ______N; FN = ______N

Show work:

m =

3) q = ____o, m = tanq; tan ___0 = _____

4a) h = ______m; hyp = _____m; sinq =h/hyp; q =_____o

4b) Fp = ____ N; show work!

FN = ____ N; show work!

Ff = _____N; show work!

Calculate the acceleration: show work and diagram!

acalc = _____m/s2 (from formula)

aexp = _____ m/s2 (from photogate)

Ea = (subtract the two accelerations: acalc - aexp