1. Atwood Machine Y

2. Newton 2 nd Law M2 = 50 g, M1 = 20 g, The Pulley is rotating to the right (clockwise) Apply Newton’s 2 nd Law to M2 and M1: M2g – T = M2a (down --- positive) T – M1g = M1a (up ---- positive) Add these 2 equations:

3. Calculate acceleration of the system Cancel the tension T: M2g – M1g = M1a + M2a (M2 – M1) g = (M1 + M2) a a = (M2 – M1) g / (M1 + M2) a = (5 – 2 ) x 9.8 / (5 + 2) a = 3 x 9.8 / 7 = 4.2 m/s^2  a (cal)

4. Find the experimental value of acceleration Place M1 in the bottom, Measure the initial height of M2 –> Y Let M2 free Fall, at the same time, start the time. Stop the watch when M2 touches down the bottom, record the time of falling – t Y = ½ a t 2 a = 2Y / t 2 sub measured Y and t  a (exp)

5. Open “Atwood Machine” on the Desktop. Make sure “velocity” is selected Place M1 in the bottom, Make sure M1 and M2 are straight, perpendicular down. Let M2 free Fall, at the same time, click start the time. Click Stop just before M2 touches down the bottom, Click “linear fit” for the Velocity – Time Graph High light the Velocity – time line, look for the Slope m- --- that is the a (exp) Find the experimental value of acceleration using Computer

6. a error% Compare calculated and experimental values of acceleration: a error% = (a (cal) – a (exp) )/ a (cal) x100% = ( 4.2 - a (exp) )/ 4.2 x100% Reference: http://brhscpphysics.pbworks.com/w/file/fetc h/50792063/Atwood.pdf