Answer:
B. use light of a shorter wavelength.
Explanation:
We know that

h= plank's constant
c= speed of light
λ= wavelength of the incident light
so, in order to have sufficient energy for for the emission of electron, the incident's radiation must have λ small enough.
B. use light of a shorter wavelength.
Due that the velocity is constant that means that friction force is equal to the force exert by you, otherwise the refrigerator will accelerate or decelerate and in both cases velocity will not be constant.
So then the friction force between refrigerator and floor is 150 Newtons.
Power used by the clock=1.03 W
Explanation:
resistance= 14000 ohm
voltage=120 V
The formula for the power is given by

P=(120)²/14000
P=1.03 W
Answer:
It is very important because scientists, especially the ones with empirical experiments and results, are prone to error and the empirical data is in need to be under strict observation done not only by many scientists but also by expermiented ones. This guards everybody to change the parameters suddenly which can affect the real results of an experiment
Explanation:
You multiply force times friction