Write the answer to this question. energy is measured in units called joules(j). suppose a roller coaster car starts with 78,000 j of potential energy. in a few seconds, it converts two-thirds of this energy into kinetic energy. as it takes a curve, the car doubles its kinetic energy. how much mechanical energy does the car now have?

78,000 J

Explanation:

Given

Initial Potential Energy P=78,000 J=78 kJ

Total Energy=Potential Energy+Kinetic Energy

initially kinetic energy is zero therefore

Total Energy=Potential Energy

If two-thirds of this energy converts to kinetic Energy

i.e. kinetic Energy

As it take curve its kinetic Energy doubles i.e.

but total Energy is constant i.e. 78 kJ

therefore there must be a decrease in Potential energy of coaster

78=104+P.E.

P.E.=-26 kJ

Mechanical Energy of car is =sum of kinetic and Potential Energy

=78 kJ=78,000 J

the answer is c. the lower legs are levers, and the knees are fulcrums. the ankles hold the loads.