You balance a 2 kg block on the palm of your hand. You then lower it, very slowly and gently, a distance of 1.0 meters.  What work do you do on the block? (in Joules)

A box of mass 2 kg is placed on the outer rim of a merry-go-round that has a radius of 6 meters. The coefficient of static friction between the box and the merry-go-round is

A plot of the velocity vs. time for a particle moving in one dimension is shown below.  The particle starts from rest at t = 0 seconds and accelerates at a constant rate until t = 2 seconds, when the velocity is 5 m/s.  The particle continues at this speed until t = 5 s and then slows at a constant rate until t = 8 s, when its velocity is zero.  What is the average velocity of the particle between 0 and 5 seconds?  

A man has a mass of 80 kg. He stands on a bathroom scale in an elevator, and the elevator moves up. As it gets close to the top floor, it slows uniformly from 4 m/s to a stop in a time of 2 s. During this time, what does the scale read (in kg)?

A particle goes in a circle in the x-y plane.  At an instant in time its velocity is  3m/s i + 4m/s j, and its acceleration is 40 m/s2 i – 30 m/s2 j.  What is the radius of the circle?

Consider trying to push a 20 kg block up a 370 frictionless incline (slope) with a force of 200 N applied parallel up the incline. What is the magnitude of the block’s acceleration?  

Which postzygotic barriers prevent formation of hybrids beyond the first generations?

In a bell-shaped curve showing the type of natural selection occurring, the y-axis (vertical direction) of the graph represents which of the following?

Use the following information to answer the question.Giardia intestinalis can cause disease in several different mammalian species, including humans. Giardia organisms (G. intestinalis) that infect humans are similar morphologically to those that infect other mammals, thus they have been considered a single species. However, G. intestinalis has been divided into different subgroups based on their host and a few other characteristics.In 1999, a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species. The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G. intestinalis and a few other morphologically distinct species of Giardia. The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species. (T. Monis, et al. 1999. Molecular systematics of the parasitic protozoan Giardia intestinalis. Mol. Biol. Evol. 16:1135-44.)By examining the phylogenetic tree diagrammed in the figure above, what conclusion can you draw about the species G. microti?

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?