Answer: to only change one factor in an experiment or test
Answer: Jupiter's mass
Explanation:
From Kepler's third law:

where T is the orbital period of a satellite, a is the average distance of the satellite from the Planet, M is the mass of the planet, G is the gravitational constant.
If the average distance of one of Jupiter's moons to Jupiter and its orbital period around Jupiter is given then mass of the Jupiter can be found:

It increases confidence because the more times you conduct the same experiment over and over should either prove your hypothesis right and wrong and eliminate any random occurrences that might affect your results.
Answer:
2100 J
Explanation:
Parameters given:
Force acting on the object, F = 420 N
Distance moved by object, d = 5m
The change in kinetic energy of an object is equal to the work done by a force acting on the object:
W = F * d
∆KE = F * d
∆KE = 420 * 5
∆KE = 2100 J
A metallic bond would be formed