Punching Bag - Embedded Physics

[hgpt]

I've got the following problem:
 

I have a ground fixed punch bag (attached to the floor using a solid base with a spring on top).
What is the minimum sensor setup in order to determine:

• the force of the punch in the bag
• acceleration of the punch
• the speed of the punches (for multiple punches)

Notes:

• no sensor must be attached on the person punching the bag, only on the bag
• bag is punched in a limited vertical area (distance between tip of the bag and punching area is constant R)

Justify the answer with:

• sensors (only sensors must be used, no webcam tracking gimmicks)
• calculations

 

I do need to mention that you know:

• the mass of the punch
• the mass of the bag
• acceleration of the bag (by using an accelerometer)
• any height can be measured