2 is B. 3 is D. 4 is C. I think 5 is A. 6 is A. 7 is D. I think you are all correct. Good Luck!
Answer: A piston-filling fountain pen has a piston — just like in a car — inside the barrel. This piston goes down to expel air or ink and then back up, pulling ink into the barrel. The typical process is very simple, assuming the pen is clean and dry: Push the piston down, expelling any air in the barrel
Hello!

Use the equation:

Where:
m = mass of the object (kg)
g = acceleration due to gravity (≈9.8 m/s)
h = height above ground (m)
Plug the given values into the equation:
PE = 7500 · 9.8 · 100
PE = 7,350,000 Joules.
Answer:
Total length of spring 0.647 m
Explanation:
We have given mass of the person m = 150 kg
Acceleration due to gravity 
Spring constant k = 10000 N/m
Nominal length of spring = 0.50
According to hook's law


x = 0.147 m
So total length of spring = 0.50+0.147 = 0.647 m