As Ali becomes caliph, the Ummayads under the leadership of Muawiya refuse to recognize him, sparking the first Muslim Civil War. The increased division leads eventually to the Tragedy at Karbala which is a defining event for Shia Muslims.
Supermassive Black Holes. Created by Sal Khan.
Supernova clarification. Created by Sal Khan.
Supernova (Supernovae). Created by Sal Khan.
In this video, learn about how the model of the foreign exchange market is used to represent the determination of exchange rates.
Surface area is the sum of the areas of all faces (or surfaces) on a 3D shape. A cuboid has 6 rectangular faces. To find the surface area of a cuboid, add the areas of all 6 faces. We can also label the length (l), width (w), and height (h) of the prism and use the formula, SA=2lw+2lh+2hw, to find the surface area.
Seeing that the surface area to volume ratio of cells generally decreases as cells get larger, making the exchange of resources, waster and heat more and more difficult.
Surface tension in water, and how the surface tension is related to hydrogen bonding.
Let's continue our fast survey of ancient history, with references to the stories from the Old Testament.
Sykes-Picot Agreement and the Balfour Declaration
When a tax is imposed in a market this is another example of government intervention. In this video, we explore the effect of imposing a tax on the price and quantity in a market. Created by Sal Khan.
A progressive tax system is a tax in which the percentage of taxes paid (the average tax rate) increases as income increases. Income is broken down into tax brackets, and each bracket's marginal tax rate increases as you move into higher brackets. Learn how to use tax brackets to calculate income tax in this video. Created by Sal Khan.
Understanding what a tax deduction is. Created by Sal Khan.
An interesting case of taxes and tax incidence is when one of the curves is perfectly elastic. Explore what happens when demand is perfectly elastic in this video. Created by Sal Khan.
The burden of a tax falls most heavily on someone who can't adjust to a price change. That means buyers bear a bigger burden when demand is more inelastic, and sellers bear a bigger burden when supply is more inelastic. Created by Sal Khan.
How to factor in negative externalities through taxation. Created by Sal Khan.
How government can effect aggregate demand through tax policy. Created by Sal Khan.
The spending multiplier and tax multiplier will cause a $1 change in spending or taxes to lead to further changes in AD and aggregate output. The spending multiplier is always 1 greater than the tax multiplier because with taxes some of the initial impact of the tax is saved, which is not true of the spending multiplier.
The science of taxonomy and where humans fit into the tree of life.
An introduction to the Technology in World War I