In the EXPLORE section of your lesson 4.08 on Potential energy there were several animations to watch that provided a graphic illustrating how the PE and KE in a system changed as a skateboarder rides a halfpipe or a pendulum moves, why did the bar for the total energy remain constant? Question 8 options:

all answers given are correct

Energy is converted from kinetic to potential and potential to kinetic, but the total amount of energy is conserved

This is because no energy is being created or destroyed in this system

Because these models do not take into account the impact of friction and air resistance and are helping to solidify the concept of energy conservation and that the total mechanical energy remains constant in that model

Many machines- including inclined planes such as ramps- increase the strength of the force put into the machine but decrease the distance over which the force is applied.

Part f - example: finding two forces (part i) two dimensional dynamics often involves solving for two unknown quantities in two separate equations describing the total force. the block in (figure 1) has a mass m=10kg and is being pulled by a force f on a table with coefficient of static friction îľs=0.3. four forces act on it: the applied force f (directed î¸=30â above the horizontal). the force of gravity fg=mg (directly down, where g=9.8m/s2). the normal force n (directly up). the force of static friction fs (directly left, opposing any potential motion). if we want to find the size of the force necessary to just barely overcome static friction (in which case fs=îľsn), we use the condition that the sum of the forces in both directions must be 0. using some basic trigonometry, we can write this condition out for the forces in both the horizontal and vertical directions, respectively, as: fcosî¸â’îľsn=0 fsinî¸+nâ’mg=0 in order to find the magnitude of force f, we have to solve a system of two equations with both f and the normal force n unknown. use the methods we have learned to find an expression for f in terms of m, g, î¸, and îľs (no n).

The solid that is formed and usually sinks to the bottom of a solution is the