Answer:
The second dart leaves the gun two times as faster than the first one.
Explanation:
Assuming no energy loss during the spring-dart energy transfer, we have by the conservation of energy principle

Given an arbitrary
and its double,
, launch velocities are

I believe that it is electric field
Answer:
I'm going to say b. gasoline is a chemical and when it combusts, it causes heat (thermal energy) and when the piston rotates because of the thermal expansion, you get mechanical force.
Temperature that will be my answer number 1
Metal
Explanation:
semiconductors are materials which have a conductivity between conductors (generally metals)