https://www.youtube.com/watch?v=2WuB8BhUJrc

1-According to the narrator and marathon participant, what is by far humans' best adaptation running distance?

a-Bigger brains

b-A longer torso

c-Legs that act like rubber bands

2-How much force did our 75 kg narrator create with each step?

a-100 lbs

b-1400 lbs

c-500 lbs

3-Because our legs act like rubber bands they store kinetic energy (mechanical energy--I quibble that it's actually stored elastic potential energy...)instead of needing to use chemical energy allows us...

a-to run faster

b-go farther with less work.

4-I am raising a 20 kg rock to a height of 1.5 m. How much force am I applying to the rock?

5-In Q1 above, what are the proper "units" for the force?

a-Joules

b-Calories

c-Newtons

d-Watts

6-Using the same problem: I raised a 20 kg rock 1.5 m off the ground, how much work did I do?

7-The unit for mechanical work is...

a-Watts

b-Newtons

c-Calories

d-Joules

8-I raised a 20 kg rock 1.5 m off the ground. I am just holding it now. Nothing is moving (except for the muscles in my back and arms that are twitching like crazy--doing work--but that's internal energy/work). So how much mechanical work am I doing now? This is a numerical answer...

9-In the scenario of me picking up the rock that we have been discussing, how much work did gravity do? Be oh so careful of those pesky +/- signs!

10-What was the net energy added to the universe by me picking up that rock?

11-How much work is gravity doing?

A man pushes a very heavy crate across a horizontal floor. The gravitational work (done by earth on the crate) ... a). depends on the weight of the load. ... b) ... cannot be calculated without more information. c) is equal to zero.

a-depends on the weight of the load

b-I need more info!

c-No work, because gravity is perpendicular to the motion.

d-I stopped caring about this.... :)