One of the most effective tool in increasing studying time is punishment and reward.
Why you like to do some thing ?
For example watching movies or playing sports. Your brain rewards you for the activities. Movies are essentially stories and they play on emotional and memory center of our brain. In return as we relive or validate our memories, our brain rewards us of certain chemicals like dopamine. These reward neurons act on pleasure center of our brain and hence we are tuned to repeat the activities.
If you want to increase productivity in terms of time involved, then you must punish your self if you miss your goal and reward your self if you fulfill it.
For example you made your time table for studying 2 hours of physics. Then you must punish yourself for not watching TV for next 30 minutes if you fail to fulfill your plan. If you complete you may reward yourself your favorite candy.
Your punishment can be reward for some one else. Suppose you say that if I don’t finish and my friend finishes , then my candy goes to him.