Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

# Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography

Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

 Choose a Topic or Enter a keyword to search: I cannot find what I want! You have selected the following Demos: None Selected

Choose a subtopic:
Measurement
Motion In One Dimension
Motion In Two Dimensions
Newton's First Law
Newton's Second Law
Newton's Third Law
Statics Of Rigid Bodies
Applications Of Newton's Laws
Gravity
Work and Energy
Momentum
Rotational Motion
Properties of Matter
Hooke's Law
Force Constant of a Spring
Spring Scale Collection
Strings and Springs
Breaking Wire (Plasticity)
Bending Beams
Prince Rupert's Drops
Shear Block
Happy and unhappy balls
video  - Coefficient of Restitution
Crystal Models

### Force Constant of a Spring

#### Purpose:

To show the relationship of the force constant, k, of a spring to an applied force and to its potential energy.

• #### Method 1:

Place the masses and holder on the spring so as to allow their weight to compress on the spring. Measure the distance that the spring is compressed. By Hooke's law, the force exerted by the spring is equal to -kx. This force is now equal, but opposite to, the weight of the masses and holder.

So: kx=mg Then: k=mg/x.

• #### Method 2:

Attach the spring and car assembly to the end of the air track and load the smaller car into the spring, engaging the release mechanism. Measure the displacement of the end of the spring, (x). Release the small car and measure its velocity by timing it through a distance. Since mechanical energy is conserved, the elastic potential energy of the compressed spring is equal to the kinetic energy of the small car.

So: 1/2kx2=1/2mv2 Then: k=mv2/x2.

#### Equipment:

• Timer
• Meter Stick
• Air Track
• Gliders w/ spring attachment
• Weight Holder
• Weights