At its natural resting length, a muscle is close to its optimal length for producing force. as the muscle contracts, the maximum force it can deliver decreases. when a muscle is at approximately 80% of its natural length, it cannot contract much more and the force it can produce drops drastically. for a muscle stretched beyond its natural length, the same is true. at about 120% of its natural length, the force that a muscle can exert against drops drastically. this muscle length to force relationship can be demonstrated by doing a chin-up. as you hang from the bar, your biceps muscles are stretched and can produce only a relatively small force. as you get close to the bar, your biceps muscles contract substantially, and you again experience difficulty. the easiest part of the chin-up occurs somewhere in between, when your muscles are close to their natural length.

While studying chemical reactions and conservation of matter, sarah's class conducted a variety of experiments. sarah and her lab partner found the mass of a wax candle and placed the candle in a flask. the students lit the candle and let it burn to completion. all that was left was wax and charred candle wick. per their teacher's instructions, the students found the mass of the products. their data can be seen in the data table. formulate a hypothesis the students could test to explain why the experiment did not support the law of conservation of matter. a) the students could repeat the experiment using different candles; there might have been a flaw in the candle. b) the experiment should be repeatable. the students should run several trials and then take an average of the after mass in each trial. c) the students should have someone in the class check their measurement skills as they repeat the experiment. they may have made an error using the balance. d) the students should burn the candle in a container that has some type of lid so that any gas that is a product of the reaction can be contained and massed. submit