AP Wednesday 30 Sep

Key concepts: Target: Two body tension: & Momentum

Journal:

1. Draw a Free Body diagram of the following demo (Rubber band & cart) at the following three points.

a. Just prior to the cart leaving my hand

b. Half way to the max displacement

c. Max displacement

2. After the cart leaves my hand, locate minimum & maximum:

a. Velocity

b. Force from rubber band & direction

3.What will happen to a Helium balloon floating in a car when the car hits it breaks?

Two body tension:

1.

Example Problem 3

A box of m₁ = 5 kg sits on a ramp of 30 degrees. It is connected, by a rope drawn through a pulley, to a box m₂ = 4.0 kg that is hanging off the side of the table.

a. What is the acceleration of the block down or up the plane?

b. Tension?

c. If the coefficient of static friction between the 4.0 kg block and the table is 0.3, find  acceleration (if the blocks move)?

Free Body (System):

                    F_x(5kg)        W_4kg

(F_s goes in opposite direction of motion)

1.   (Solve acceleration for System)

a.    F_net= ma  --> 

    W_4kg -  F_x(5kg)           =  ma       (System)

   40N - (Sin 30)(W_5kg)   =  (9kg)a

  40N - (.5)(50N) =  (9kg)a

a = (40N -25N) / 9kg   -->  1.7 m/s²  (up the plane)

b. Tension:  isolate one block (i.e., 4kg)

F_net= ma  -->  W_4kg -  T   =  m_4kga

40N - T  =  (4kg)(1.7 m/s² )

T  =  (4kg)(1.7 m/s² ) - 40N = 33.2N

c. Acceleration with friction:

F_net= ma 

-->  W_4kg -  F_x(5kg) -  F_s(5kg)   =  ma  

        W_4kg -  F_x(5kg) -  (m)F_N =  ma  

 40N - {(Sin 30)(W_5kg) + (m)(Cos30)(W_5kg)}  =  (9kg)a 

           40N - {(25) + (.3)(43.3)} = (9kg)a

            40N - {(25) + (13)} --> (9kg) a

            a  = 2N/9kg  = 0.22m/s² (moves up the incline)  

Wed 6 Oct  Lab#4: Ball Toss

Tues 12 Oct Lab#5: Unknown Mass