A little over 10.25 grams of pure silver.
A silver fifty cent piece weighs about 12.5 grams.
1949 would be a Franklin half dollar, which weighs 12.5 grams and is 90% silver, giving it 11.25 grams of silver per coin. It's currently (as of 7 September 2012) worth about $12.
It really depends on the date and condition.
A U.S. fifty cent piece dated 1961 is a Franklin half dollar. The coin is not rare, if it shows any wear the value is about $12.00 just for the silver.
About $2.00 only for the silver.
14oz
About $12.00
A '60 Franklin half is worth about $11-12.
1966 Kennedy half dollar is 40% silver and valued at about $2.50 for the silver.
The coin has NO silver and is face value.
A US fifty cent coin, or half dollar, is 30.6 millimeters in diameter. Weights of these coins vary depending on year of mint--previous to 1965 the weight is 12.5 grams. 1965 to 1970 the weight is 11.5 grams, and from 1971 forward they weigh 11.34 grams.
One cent (minted 1982-present) weighs 2.5 grams. 50 of them weigh 125 grams.