Answer:
a.

Explanation:
a. Find the probability that exactly one photo detector of a pair is acceptable:
Let
photo is accepted and the probability
is defected.
Therefore:

#The probability of exactly one photo detector of a pair is accepted is 7/25
b.Find the probability that both photo detectors in a pair are defective,P(D1D2):

Hence, from out tree diagram,the probability that both photo detectors in a pair are defective is 6/25
Answer:
Spring constant, k = 24.1 N/m
Explanation:
Given that,
Weight of the object, W = 2.45 N
Time period of oscillation of simple harmonic motion, T = 0.64 s
To find,
Spring constant of the spring.
Solution,
In case of simple harmonic motion, the time period of oscillation is given by :

m is the mass of object


m = 0.25 kg


k = 24.09 N/m
or
k = 24.11 N/m
So, the spring constant of the spring is 24.1 N/m.
So the equation for angular velocity is
Omega = 2(3.14)/T
Where T is the total period in which the cylinder completes one revolution.
In order to find T, the tangential velocity is
V = 2(3.14)r/T
When calculated, I got V = 3.14
When you enter that into the angular velocity equation, you should get 2m/s
They cause an increase in temp of earths atmosphere or warming by absorbing solar energy. hope this helps