Example 

The diagram shows the displacement-time graph for a body performing simple harmonic motion. Suggest in terms of period T the following
(a)    range of time where the velocity and acceleration are in same direction.
(b)    range of time where the velocity and acceleration are in opposite directions

suggested answers

$\genfrac{}{}{0.1ex}{}{T}{}$ 4 < t < T 2 a n d 3 T 4 < t < T

$0$ < t < T 4 a n d T 2 < t < 3 T4

Solution:

Model:

http://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejss_model_SHM12/SHM12_Simulation.xhtml