Mechanics
M-D1 : Block on Plane (I)
Unit
Dynamics in 1-dim; static friction
Purpose
Illustrate the variability of static friction, the concept of maximum static friction.
Equipment
- Small inclined plane of adjustable angle
- Assorted blocks of different surfaces, shapes
Suggestions
For one block, demonstrate that static friction adjusts to circumstances up to a fixed, maximum value (experimentally nearly fixed, maximum angle). Use different blocks to show that the coefficient of static friction is mass independent, but depends on the quality of touching surfaces.
Discussion
- While the incline is being raised the static friction force increases
- Maximum height at which the block still doesn't slide
- Block slides down (kinetic friction)
M-D2 : Block on Plane (II)
Unit
Dynamics in 1-dim; kinematic friction
Purpose
Illustrate the concept of coefficeint of kinematics friction
Equipment
- Incline plane (a flat plank & support)
- Assorted blocks of different surfaces, shapes
Suggestions
Using two sliding blocks in each run to compare the magnitude of kinematic friction, demonstrate dependence on mass (not dependent) block surface for several fixed angles.
Discussion
- Equipment
- Block Stationary, static friction at 5N
- Block Stationary, static friction increased to 9N
- Block stationary, static friction increased to 10N
- Block begins to slide, kinetic friction at 4N
M-D3 : Ball and String II
Unit
Dynamics in 2 dim, circular motion
Purpose
- Illustrate various kinds of circular motion
- Demonstrate that the string tension provides the needed centripetal force
Equipment
A ball with a long string attached
Suggestions
Demonstrate circular motion
- Whirling in horizontal
- Whirling in vertical
- Pendulum motion
- Discuss the tension in each case, noting that it depends on the position in case 2 and 3, and would be infinite in case 1 if one could whirl the string in a horizontal plane.
- Ask what would happen to the ball if the required tension exceeded the maximum tension of the string in each case 1-3
Discussion
Requires a full discussion of circular motion, including tangential and perpendicular (radial, centripetal) acceleration
M-D4a : Atwood Machine
Unit
Dynamics, simple machines
Purpose
Companion to At wood Machine problems
Equipment
- Large pulley on a stand
- String and asorted weights
Suggestions
- Demonstrate equilibrium with equal weights
- Compare motion of ml, for m1>m2, with the free fall of m3=m1-m2
- Illustrate the effects of changing m1 or m2 by equal amounts
Discussion
- Set-up in equilibrium
- Adding a small weight to upset the equilibrium
- The masses accelerate with the one on the right going down
M-D4b : Extended Atwood Machine
Unit
Dynamics, Torque
Purpose
To compare torque with the weight on each pulley
Equipment
- Fixed pulley assembly with 2 or more pulleys
- String and assorted weights 聽
Suggestions
- Demonstrate torque with different weight on each pulley
- Compare weight on pulley one with weight on pulley two
- Illustrate the change of weight on either of the pulleys
Discussion
- Equilibrium with 100g at r=7.2cm and 360g at r=2.0cm
- Non-equilibrium with 100g at r=7.2cm and 300g at r=2.0cm; pulling 300g down
- Just before release
- Masses accelerating with 100g (on the right) moving down
M-D5 : Torque Balance
Unit
Introduction to rotational dynamics
Purpose
Develop understanding of the torque as the rotating effect of a force
Equipment
- Meter stick with pivot and hooks
- A stand
- Assorted weights
Suggestions
- Single mass, vary the lever arm
- Two unequal masses, same lever arms
- Two equal masses, different lever arms
- Different masses, different lever arms (when in equilibrium?)
Discussion
- Set-up (hangers with no additional masses)
- Equilibrium, with two 200g masses
- Same as above with masses further apart
- Equilibrium, 100g on left and 200g on right
- Equilibrium, 100g on left and two masses, 100g and 50g, on the right
M-D6 : Stick and Puck
Unit
Introduction to rotational dynamics
Purpose
Develop understanding of the torque as the rotating effect of a force
Equipment
- Meter stick with pivot and hooks
- A stand
- Assorted weights
Suggestions
- Single mass, vary the lever arm
- Two unequal masses, same lever arms
- Two equal masses, different lever arms
- Different masses, different lever arms (when in equilibrium?)
Discussion
- Aiming the puck at the center of the stick (in the perpendicular direction)
- After the collision
- Aiming the puck at the end of the stick
- After the collision
