Honors Physics completed their discussion of simple machines. We reviewed the types of simple machines, described how they functioned to make work easier and the two formulas for mechanical advantage. Added in the concept of efficiency emphasized the connection between the action of many of the simple machines and the concepts we've been covering in the rotational motion unit. Tomorrow, a lab that takes us back to centripetal force and tangential velocity. Wednesday, review and Thursday will be exam day.
Physics B conducted a lab investigation on rotational equilibrium. Setting up balanced torques for a variety of masses demonstrated clearly that force (weight) was not the only player in the game. Lever arm is critically important and rotational equilibrium is dependent not on balanced forces but on balanced torques. Tomorrow, we'll discuss the lab in more detail before continuing on with our discussion of rotational inertia and angular momentum.
Physics F spent time with rotational inertia and applied that idea to rolling. How easily an object rotates or rolls depends on its moment of inertia, and that depends on the object's mass and the distribution of that mass around the rotational axis. For single objects, there are often several axes around rotation can occur, but it is easier for some than for others. We looked at some moment of inertia formulas for simple shapes and it became clear why for a hoop and a ball, with identical masses and radii, the ball would always win a race when propelled by the same force - smaller moment of inertia = easier rotation.
Physical Science took time to discuss laboratory write ups. There's been problems in that area, so with the lab we just completed as a guinea pig, we looked at what each section of the lab write up should contain and what needed to be done to the current labs to bring them up to code. Work on your rewrites tonight and let's see how things look tomorrow.
Homework
Honors Physics: 8.4 Section Review and p. 308 #39 - 43
Physics B: None
Physics F: p.165, 166 in packet #7-13 and 27-30
Physical Science: Rewrite lab write ups for simple machines labs
12/6/10
12/3/10
They See Me Rollin'
They calculate my moment of inertia...
Honors Physics went over their work on angular momentum and angular kinetic energy before moving on to simple machines. In grade 9, we lumped simple machines in with the work and energy chapter and that's fine. Both arenas, rotational motion and work are good ways to evaluate machines. We defined machines and began to look at how they functioned to make work easier. Actual and ideal mechanical advantage were contrasted and we will pick up with the families of machines and efficiency on Monday.
Physics B and F went over their torque work before beginning a discussion of rotational inertia. Objects do resist changes in rotation, but mass is not the only player. The distribution of mass is also important. Clustering mass around the rotational axis produces a lower rotational inertia than placing the mass at a distance from the axis. We'll build on this next week. On Monday, B's long block, look forward to a lab dealing with rotational equilibrium.
Physical Science got time in class to work on test corrections. Students can earn up to a maximum of 1/3 the points they missed back on their score. Next week, talking about lab write ups and continuing on with work and power.
Homework
Honors Physics, Physics B and F: None
Physical Science: Complete test corrections (if you get completely stuck on one, remember to ask me in class on Monday)
Honors Physics went over their work on angular momentum and angular kinetic energy before moving on to simple machines. In grade 9, we lumped simple machines in with the work and energy chapter and that's fine. Both arenas, rotational motion and work are good ways to evaluate machines. We defined machines and began to look at how they functioned to make work easier. Actual and ideal mechanical advantage were contrasted and we will pick up with the families of machines and efficiency on Monday.
Physics B and F went over their torque work before beginning a discussion of rotational inertia. Objects do resist changes in rotation, but mass is not the only player. The distribution of mass is also important. Clustering mass around the rotational axis produces a lower rotational inertia than placing the mass at a distance from the axis. We'll build on this next week. On Monday, B's long block, look forward to a lab dealing with rotational equilibrium.
Physical Science got time in class to work on test corrections. Students can earn up to a maximum of 1/3 the points they missed back on their score. Next week, talking about lab write ups and continuing on with work and power.
Homework
Honors Physics, Physics B and F: None
Physical Science: Complete test corrections (if you get completely stuck on one, remember to ask me in class on Monday)
12/2/10
Circular Motion Continues
Honors Physics took time to review and refresh their problem solving skills for rotational equilibrim before moving on to other properties of rotational motion - angular momentum, Newton's 2nd law applied to rotational motion and rotational kinetic energy. The concepts are familiar, they are now simply applied to rotating bodies. For problem solving, here's a hint (especially for conservation of energy problems): ω = vt/r...
Physics B and F reviewed their torque homework and spent time working with the idea of rotational equilibrium. The problem set for homework will make you think, so here's your hint: Sometimes you need to look at both conditions for equilibrium to be able to solve a problem.
Physical Science completed their simple machines lab. Little problem following directions for the lever piece, but everyone finally pulled together a good set of data. Get the writeups completed (along with your examples of the three classes of levers) for tomorrow so that we can use the information to illustrate our discussion of work and power.
Homework
Honors Physics: 8C #1, 2; 8D #1, 3; 8E #1, 2
Physics B: Torque practice problems packet
Physics F: Ancillary packet p. 165-166 #1-4, 21-23 and Torque practice problems packet
Physical Science: Complete lab write up
Physics B and F reviewed their torque homework and spent time working with the idea of rotational equilibrium. The problem set for homework will make you think, so here's your hint: Sometimes you need to look at both conditions for equilibrium to be able to solve a problem.
Physical Science completed their simple machines lab. Little problem following directions for the lever piece, but everyone finally pulled together a good set of data. Get the writeups completed (along with your examples of the three classes of levers) for tomorrow so that we can use the information to illustrate our discussion of work and power.
Homework
Honors Physics: 8C #1, 2; 8D #1, 3; 8E #1, 2
Physics B: Torque practice problems packet
Physics F: Ancillary packet p. 165-166 #1-4, 21-23 and Torque practice problems packet
Physical Science: Complete lab write up
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