Blog

Barrier islands gradually migrate further over time.

How many distinct permutations are there of the letters in the word “HAWAII”?

A man standing on a frictionless rotation platform holds a wheel by its axis with his right hand, as shown. Initially, the wheel is not rotating and he is not rotating on the platform. If he exerts a force on the rim of the bike wheel with his left hand causing it to turn counterclockwise as seen from below, what else will happen?

Assume α=4, β=λ=2.  The lifetime (in years) for a certain type of batteries has a gamma distribution with parameters α and  β.  Randomly select 100 batteries. What is the expected number of batteries whose lifetimes are at most 2λ years?

In an experiment to develop a self-inflating balloon, citric acid and baking soda (sodium bicarbonate) are mixed to generate carbon dioxide gas.  The gas inflates the balloon. 20.0 mL of 0.50 M citric acid solution was placed into seven identical bottles.  The volume of sodium bicarbonate solution was varied as shown in the plot below. The volume of CO2 generated in the balloon was measured and plotted versus the volume of 0.50 M sodium bicarbonate solution used in each trial. Based on the graph, complete the following statements: Between 0 and 20 mL, increasing the volume of sodium bicarbonate solution causes the CO2 volume to [drop1] The maximum volume of CO2 generated is [drop2] The limiting reactant at 25 mL is [drop3]. At 25 mL, there is leftover [drop4] when the reaction is complete.

The following observations are the delivery times (in days) for ten randomly selected international packages.                8,   9,  14,   9,   9,  16, 12,   5,  19,  11. Find the sample median.

Assume that random variable X is continuous with the following probability density function                     

The spinning blade of a food processor slows its rotation to 1200 rpm (revolutions per minute) after a period of 0.800 s when it had angular acceleration of –88.0 rad/s2. What was its angular speed at the beginning of the 0.800 s period?

Python’s Global Interpreter Lock (GIL) means

A moon orbits its planet with a period of 13.464 days and a semi major axis of 583,450 km. What is the mass of the planet? Assume the moon is much less massive than the planet.