2023SPp1q3 What is the air resistance when the speed is doubled?

This question is challenging to students as there are many information given. But it is actually quite straight forward when you save one thing at a time.

In this question, it is given that speed doubles, air resistance increases by four times. The actual relationship is speed is directly proportional to speed^2.

This question can be more challenging if this is given instead or that a random other speed is given. Watch the second part of the video to understand this deeper, especially for Pure Physics students.

What the video tutorial.

Question: 2023SPp1q3

Answer: Option A

Ohm's Law, ohmic and non-ohmic conductors - Quick Revision

Heating and Cooling Curves (updated)

Internal energy of a substance is the sum of kinetic energy and potential energy of the molecules.

• kinetic energy is directly proportional to the temperture of the substance

• potential energy is related to the average spacing between the molecules (PE increases as spacing increases)

  - (for O-level, we can simplify it and treat it as PE will only change when there is a change of state. E.g during melting, the intermolecular forces are overcome and molcules are further now, hence PE increases. During melting, temp remains constant, hence KE remains the same)

• - i.e at any time, there is only either KE or PE change during the heating or cooling curve.

As the substance is heated:

• energy is transferred into the internal store of the substance.

• internal energy increases.

As the substance is cooled:

• energy is transferred out of the internal store of the substance.

• internal energy decreases.