Wednesday 27 Oct:

Target: SHM

Journal:

1. A mass on a spring undergoes SHM.  When the mass is at maximum displacement from equilibrium,

a. its instantaneous acceleration (max or min)

b. its instantaneous velocity is (max or min)

c. its net force is (max or min)

d. its PE is (max or min)

e. direction of acceleration

 

 

 

 

 

 

 

 

 

 

 

  a) maximum

 b) minimum

 c) maximum

d)  maximum

e) Toward the rest point

 

2. A mass undergoes SHM with an amplitude of 10.0 cm.  The energy is 20.0 J at this time.  The mass is cut in half and the system is again set in motion with amplitude 20.0 cm.  What is the energy of the system now?

 

 

 

 

 

 

 

 

 

 

W = DPE = 1/2kx2

 

8 = 1/2kx2  

8 = 1/2k(.1)2   

k = 1,600 N/m

 

 

(mass is not a factor in PE of a spring - just k & x)

 

      W = DPE = 1/2kx2

W = E = 1/2(1,600 N/m)(.2)2

       E =    32.0 J


 

3. Increasing the amplitude of a vibrating mass-and-spring system by  3 times the distance produces what effect on the system’s mechanical energy?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

W = DPE = 1/2kx2

 

 

 Increases the energy by a factor of 9

 

 

Activity:

  • Predict/Calculate a pendulum that has a period of 1.0s  & 2.0s

  •   Make the pendulum and verify the period (average 10 cycles)

  • Turn in paper with % error (between prediction and actual).