"How to Get Your Child Motivated to Study" is a great question. As a father of four (two are now in college and two are in high and middle school), I've been blessed with kids who want to learn.
The key, in my opinion, is that the parents need to be excited about education themselves. That is, when the child sees the parent reading a book or solving a problem or learning something new -- and when the parent demonstrates a genuine enthusiasm for such learning -- then the child picks up on that enthusiasm.
You can't tell a child that he or she needs to study simply to get good grades. That's not enough of a motivation. The child needs to see that you are imbued with a love for education, a lifelong quest for learning.
For example, a few years ago I decided I wanted to learn Chinese. I began studying it, and soon my kids became interested in the Chinese language as well. My kids see me reading books, writing books and stories, trying to learn to play new songs on the piano, etc.
As an aside, I should mention that the television set in our house is OFF unless we are sitting down together to watch something educational.