1) Refraction
2)Reflection
3)Concave
4)Convex
I took the test and got this right so you can believe me :)
Hope this helps
Answer:
A) 
B) 
Explanation:
Given:
mass of car, 
A)
frequency of spring oscillation, 
We knkow the formula for spring oscillation frequency:




Now as we know that the springs are in parallel and their stiffness constant gets added up in parallel.
<u>So, the stiffness of each spring is (as they are identical):</u>



B)
given that 4 passengers of mass 70 kg each are in the car, then the oscillation frequency:



Answer:
65
Explanation:
The resonant frequencies for a fixed string is given by the formula nv/(2L).
Where n is the multiple
.
v is speed in m/s
.
The difference between any two resonant frequencies is given by v/(2L)= fn+1 – fn
fundamental frequency means n=1
i.e fn+1 – fn = 390 -325
= 65