Tommy pushes a 40 kg crate along a rough surface with 90N of force. He observes that it is only accelerating a a rate of 200 km/s. What must the value of the force of friction be? (Assume the only two forces acting on the
object are friction and Derek)

Awalk up the phase change graph worksheet

(a) calculate the number of electrons in a small, electrically neutral silver pin that has a mass of 10.0 g. silver has 47 electrons per atom, and its molar mass is 107.87 g/mol. (b) imagine adding electrons to the pin until the negative charge has the very large value 1.00 mc. how many electrons are added for every 109 electrons already present

Compare the horizontal displacement of the two balls as they travel to the ground. what do you observe?