A particle has 37.5 joules of kinetic energy and 12.5 joules of gravitational potential energy at one point during its fall from a tree to the ground. An instant before striking
the ground, how much mechanical energy.

Hi there!

Mechanical Energy = Potential Energy + Kinetic Energy, or:

E = U + K

Plug in the given potential and kinetic energies:

E = 12.5 + 37.5 = 50 J

carla slowed down in the beginning of her trip, stopped, and then sped up

depends on what you mean by "group." for order, it would be coleoptera (beetles). for class, it would be insecta (insects). for phylum, it would be the arthropoda (animals with jointed exoskeletons).

explanation: