Phy 201
Your work so far looks good. The best gauge of your progress will be your performance on Test 1, but right now everything looks fine.
On a side note fom class the fastest velocity that is attained from a rifle is in a .22-243 Middlestead, which generates 5278 feet pr second. Which is from pushing a 30 gr Hollow point bullet with 50 gr of powder, that has a high burn rate. pretty hot!
So mass m of powder will accelerate mass .6 m of bullet to about 1600 m/s.
At about 2 * 10^7 J / kg of powder, if all the energy went into the bullet we would expect a velocity of nearly 6 * 10^3 m/s, so only about (1.6 / 6)^2 = .07 of the powder's energy goes into the KE of the projectile. The rest goes into the KE of the exploded powder and into thermal and other dissipated energy.
Does gr stand for grains or grams? My guess is grains.
Can you show us in class exactly what they do to get the spaceship into orbit on the computer program tommorrow?
We might look into that Friday. It would make a good lab to see if anyone can achieve orbit with the energy available in the fuel.
phy 201
On the quiz I missed this question: If you do positive work to stretch or compress a spring, then the spring will be in a position to do positive work if it is released and allowed to return to its original configuration.
Selected Answer: false
Correct Answer: true
I I pull the spring apart and do positive work on it, when it pulls back into shape it would be doing negative work against me.
The force being exerted by the spring would be in the direction of its motion, so the force it exerts would be doing positive work.
The force you are exerting on it would be opposite its direction of motion, so you would be doing negative work on it.
Whick is positive work done on it. Is that correct, and is that what the question was asking?
Thanks,