Today we talked something about WORK AND ENERGY.
We define kinetic energy, gravitational potential energy, and the potential energy stored in a compressed or stretched spring. If all forces are conservative, the mechanical energy of an isolated system is constant. If non-conservative forces are present, we use the work-energy theorem to equate the work done by the non-conservative forces and the change in mechanical energy. (http://theory.uwinnipeg.ca/physics/work/index.html)
we handed in a lot of stuffs like:
1) Centripetal Acceleration & Force assignment
2) Test w/ correction
3) Lab about centripetal force
Thank you Mary I copy your blog. I think somebody didn't done it, so post it again.
what we need to do today is
1)READ PAGE 101 （the green book)
2)READ UP PAGE 323-330 (DUCK BOOK)
3)DO PROBLEMS PAGE 330 1--6 (DUCK BOOK)
If you didn't take the book to home, that 's OK . I post the questions for you guys.
1. Determine the work done in each of the following cases:
a) Kicking a soccer ball forward with a force of 40N over a distance of 15 cm
b) Lifting a 50-kg barbell straight up 1.95m
c) Pulling a sled with a force of 120N at an angle of 25 degrees to the horizontal if the sled
is displaced 4.0m forward
2. A tow truck pulls a 3000-kg car form rest with a horizontal force of 5000N. The truck and
car accelerate at 2.5m/s^2 for 5.0s to reach the speed limit of 45 km/h. How much work
is done by the tow truck?
3. A wheelbarrow is pushed by a force of 78N [U 35 degrees R] over a distance of 10m. Determine the work done to move the wheelbarrow along the ground.
4. A 52,000-kg train slows form 25m/s to 14m/s in 5.0s. Calculate the work done on the train.
5. Calculate the work done in each of the following graphs
6. Determine the height form which a 3-kg axe must be dropped so that it does 480J of work to split a log resting on the ground.
In the final, I want to show you guys some videos, but I don't know how to do it. I just give you the address.
http://www.youtube.com/watch?v=2WS1sG9fhOk&feature=related
next one is Tan LM.
see you guys tomorrow
1 comment:
Very good post, Hao. Thanks for putting the questions on the blog for everyone to see.
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