## Key Announcement: MS1 is Tomorrow at 8am in computer room

## Worked Problem

Similar to Knight vs 4 question 9.59. A horizontal spring (k=250 N/m) is compressed 12 cm and a 250g box is placed at the end of the spring. If the coefficient of kinetic friction between the box and the floor is (f

_{k}=0.10), What is the box's maximum speed? (Solve 2 ways...)

Question: Why would this be a difficult problem for Newton's approach?

Potential, Thermal, Kinetic Energy Click to Run |

## Key Ideas

ΔE_{sys} = ΔK + ΔU + ΔE_{th} = W + Q

- if Q=0 & W=0 → isolated system
- if Q=0 & W=0 & ΔE
_{th}=0 → isolated, nondissipative system

F(s) = - dU/ds

Forces: conservative vs non-conservative

## Thinking Steps

- Picture
- Choose System/Environment
- FBD if needed.
- Solve noting energy

## PPT (Ref: Knight Ch 10)