Week 2 Lecture 3
Solutions at the bottom.

1)  In-video quiz at timepoint 02:40.

Consider a car moving north at 10 meters per second (m/s). If the car slows to 4 m/s north in 3 seconds, what is its acceleration?

a) 6 m/s2 south
b) 2 m/s2 north
c) 6 m/s2 north
d) 2 m/s2 south

2)  In-video quiz at timepoint 10:11.

"In physics and all science, dimensional analysis is the analysis of the relationships between different physical quantities by identifying their dimensions. The dimension of any physical quantity is the combination of the basic physical dimensions that compose it, although the definitions of basic physical dimensions may vary."
Wikipedia - dimensional analysis, http://en.wikipedia.org/wiki/Dimensional_analysis
http://www.chem.tamu.edu/class/fyp/mathrev/mr-da.html

In order to understand centripetal acceleration>, the concept of centripetal force should be referred to. 
http://en.wikipedia.org/wiki/Centripetal_force#Local_coordinates
http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/shawna_sastamoinen/Centripetal.htm

"Magnitude is the logarithmic measure of the brightness of an object, in astronomy, measured in a specific wavelength or passband, usually in optical or near-infrared wavelengths".
Wikipedia - magnitude (astronomy), http://en.wikipedia.org/wiki/Magnitude_(astronomy)

Solutions:

1) Correct answer is d) 2 m/s2 south

The change in velocity is 6 meters per second. The change in time is 3 seconds. Therefore the magnitude of the acceleration is 6 / 3 = 2 meters per second squared (m/s2 ). The direction of the acceleration is south because the north-moving car is slowing down. If the car had sped up to 16 meters per second, the magnitude of the acceleration would have been the same, but the direction would have been north, not south.\