Sunspots are regions of much higher magnetic field, and lower temperature, on the surface of the sun. They occur in an eleven year cycle, and effect our planet through the solar wind.

# Category Archives: Preliminary

# Star temperature and light

When things are at different temperatures they emit different wavelengths of light, for example a piece of steel will pass through a number of colours as it is heated. The same is true of stars, and of the entire electromagnetic spectrum (not just visible light). We can use this fact to determine the temperature of the star.

# HR diagrams

The Hertzsprung-Russell (HR) diagram is a scatter plot of star magnitude against star brightness (there are other equivalent axes which are also used). It is a very useful way of grouping stars and plotting their evolution.

# Kinetic energy and work

Energy is a significant quantity in all branches of physics, largely because it is conserved. These slides introduce energy, specifically the kinetic energy of a moving object. The conservation of energy is used to relate kinetic energy to ‘work’. Work is a measure of how much energy is associated with the action of a force. Some questions are also included.

# Mass and weight

These brief slides explain the difference between mass (measured in kilograms) and weight (which is a force, measured in newtons). Some relevant questions are also provided.

# Circular motion

These slides give a quick overview of centripetal (and centrifugal) force, as well as a few questions applying these concepts. Equations for centripetal force and centripetal acceleration are given.

# Adding Vectors

The addition of vectors is very useful for solving problems when more than one vector is involved in a calculation. This would include situations where multiple forces are acting, situations where we consider multiple velocity components, and situations where an object is displaced more than once.

Vector addition allows us to reduce *many vectors* into *one equivalent vector*, thus simplifying the problem to be solved. These slides outline vector addition and apply it to Newton’s second law. Sample problems are provided to determine the resultant force (net force), resultant velocity and total displacement.