Physics 12 Mr. Jean January 6 th, 2012

The plan: Video clip of the day. Visiting the relatives How mass increases with speed. Finish (Faster than the speed of light) –Parts #3 & #4

Time Dilation Formula:

Length Contraction:

Mass of a particle at rest: The mass of a particle when it is at rest is m o. This is called the rest mass of the particle.

Einstein showed that the mass of an object increases with its velocity according to the equation.

The equation above shows that the mass of the particle increases with its velocity, and approaches infinity at the speed of light. Einstein said that nothing could travel faster than the speed of light.

Einstein also redefined momentum and energy. The new equation for momentum is

The new equation for the total energy is: This can be written as:

Visiting the relatives

Important Note: The astronaut would see herself at rest with the rest of space zooming past her. Thus, lengths are shorter and contracted for Astronaut.

Visiting the relatives Earth would see the actual length. So we would expect this length to be larger.

Visiting the relatives

Visiting the relatives: B) Relative to the Earth observer, more time would pass than passes on the moving spacecraft.

Visiting the relatives: C) Now, we can calculate the astronauts speed using the astronaut’s observations.

Visiting the relatives: D) Calculate the observed speed from Earth by using the Earth’s observer’s calculation.

Visiting the relatives E) The identical answer will tell us that the speeds are the same when measured by either observer. This is a result of both the Earth observer and the astronaut using their own observations of distance and time, which do differ.

Chapter 16 Topics: Right Hand Rules AC & DC Motors (Basic concepts & Force) AC & DC Generators Lenz Law Transformers (Step up & Step down)

Chapter 17 Topics: Time Dilation Length Contraction Mass Change Total Energy Change Momentum Change