Question

energy transformation pe ke
if an object has 100 joules of potential energy (pe) at the top of a ramp,
how much kinetic energy (ke) will there be at the bottom (no energy
is lost, and any item on the ramp has no friction between the ramp)
a 0 j and 100 j
b 50 j and 0 j
c 50 j and 100 j
d 100 j and 0 j
in the first question, we described an energy - transformation in a
situation without friction. in reality, we almost always must contend
with friction when analyzing energy transformations. how would the values
change and why?
a the ke value would decrease. friction causes some
of the energy to be lost.
b the pe and ke values would both decrease due to the
presence of friction. friction opposes motion.
c the ke value would increase. friction causes some
of the energy to be converted to heat energy.

Explanation:

Step1: Recall energy - conservation principle

In the absence of non - conservative forces (friction, air resistance etc.), the total mechanical energy $E = PE+KE$ is conserved. At the top, $E = PE_{top}+KE_{top}=100 + 0=100\ J$.

Step2: Calculate $KE$ at the first lower level

At the first lower level, $PE = 50\ J$. Using $E = PE + KE$, we have $100=50 + KE$. Solving for $KE$ gives $KE=100 - 50=50\ J$.

Step3: Consider the second lower level

At the lowest point, if there is no friction, all of the initial potential energy is converted to kinetic energy (since $PE$ is minimum at the lowest - point). So $PE = 0\ J$ and $KE = 100\ J$.

The answers for the first part are: At the first lower level, $PE = 50\ J$ and $KE = 50\ J$; at the lowest point, $PE = 0\ J$ and $KE = 100\ J$.

For the part about friction:
Friction is a non - conservative force. It dissipates energy in the form of heat. The total mechanical energy $E=PE + KE$ decreases. Since the initial total mechanical energy is fixed, when friction is present, some of the energy that would have gone into kinetic energy is lost as heat. So the kinetic energy value would decrease.

Answer:

For the energy values: At the first lower level: PE = 50 J, KE = 50 J; At the lowest point: PE = 0 J, KE = 100 J
For the friction part: A. The KE value would decrease. Friction causes some of the energy to be lost.