Redemption Time

After the Physics practical paper, there was an exodus of students from college back to their hometowns. At this point of time, most of you have found your way back to the college preparing for the next battle. If you feel that you didn't do that well in your practical, this is the time for you to redeem yourself.

In "deformation of solid", be careful of the axis of the graphs. It can be "force against extention" where area under the graph gives the work done or the strain energy stored. The gradient of the straight line is the force constant. If the graph is "stress against strain", then the gradient of the straight line portion gives Young's modulus and the area under the graph yields energy density. Be careful, energy density is NOT "1/2 X stree X strain" because not all areas are in the shape of a triangle.

Make sure you know the difference between "limit of proportionality" and the " elastic limit".

From "stress-strain" graph:

1. Gradient of straight line tells you whether the material is stiff or flexible.

2. No curve or very short curve means that the material is brittle and not ductile.

3. Strong means has higher ultimate tensile stress.

4. Tough means the area under the graph ( with the curve or plastic region ) is bigger.

You can "work harden" steel by repeatedly beating it with hammer or roll it repeatedly. It makes the steel stronger, harder but more brittle. Work hardening increases the no of dislocations.

Make sure you know the various type of composites, namely particle composite and fibre composite. Know at least one example of each type of composite.

These are some of the points that come to my mind as I write this. They are by no means exhaustive. Revise well and you will be confident when you enter the examination hall.

Lastly, "Good Luck to ALL of you".