Sally travels by car from one city to another. she drives for 26.0 min at 81.0 km/h, 46.0 min at 30.0 km/h, and 46.0 min at 52.0 km/h, and she spends 11.0 min eating lunch and buying gas.
a) determine the average speed for the trip.

(b) determine the total distance traveled.

the answer is b, have negligible mass

chemical energy --> gravitational potential energy --> kinetic energy --> elastic potential energy --> gravitational potential energy

explanation:

when emma starts the hike, the chemical energy stored in her body is used to climb up the mountain, and so she gains gravitational potential energy (because at the end, she will be at a higher height h above the ground). then she goes bungee jumping: as she falls, this gravitational potential energy is converted into kinetic energy (because her speed increases as she falls down), until the point when the rope stretches, and she stops moving. at that moment, all the kinetic energy is converted into elastic potential energy due to the stretching of the rope. then, this energy is released because the rope returns to its natural length, and emma gains a small increase in altitude , so she gains some gravitational potential energy.