# Tutor profile: Sean C.

## Questions

### Subject: Product Design

I am struggling with the button feel for my project, I can update the overall CAD of the design but I must stay within my current package size, what is the best way to achieve this?

My advice would be to first look at the materials you are using in your button design. Sometimes this can be fixed by simply changing the durometer of the rubber in your button to get the necessary pre-load you need on your switch. Another solution could be to use a composite button that has a stiff plastic material on the end of it to give a firm surface to press the switch all the way in when the button is actuated.

### Subject: Mechanical Engineering

What does my textbook mean when it asks if my material has undergone strain hardening?

Strain hardening occurs when in the plastic region of the stress strain curve before the material hits its ultimate strength. If a design goes plastic while place under a load but does not hit the ultimate strength of the material it will follow back down the stress strain diagram a the same rate (young's modulus) that it increased in the elastic region. This effectively increases the materials yield strength

### Subject: Calculus

I need help with related rate problems, please see the example below: You are 200 miles away from a train. The train is traveling towards you at 30 mph, you are traveling towards the train at 5 mph. How long will it take for the distance between you and the train to be 125 miles.

In order to solve a related rates problem the first step is to interpret the problem statement into an equation. Let's start by doing this symbolically and then plug in the numbers later. Let dt/dx = the rate the train is moving Let dy/dx = the rate you are moving Let t = the time that has elapsed Let Xi = the initial distance between you and the train let Xf = the final distance between you and the train In order to get the final distance you must take your initial distance and subtract the distance that both you and the train have move towards each other over the same amount of time. In equation form: Xf = Xii-(t*(dt/dx+dy/dx)) From here you should be able to plug in the numbers and solve for t and get the answer to be 2.14 hours

## Contact tutor

needs and Sean will reply soon.