9. If the frequency of a certain light is 3.8 x 10 Hz, what is the energy of this light?
1 answer:
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Answer:
Explanation:
mass of car, m = 1022 kg
mass of truck, M = 1620 kg
initial velocity of truck, U = 14.5 m/s
initial velocity of car, u = 0 m/s
Let the final velocity of car is v and the final velocity of truck is V.
Collision is elastic, so the coefficient of restitution, e = 1
Use conservation of momentum
initial momentum of car + initial momentum of truck = final momentum of car + final momentum of truck
m x u + M x U = m x v + M x V
0 + 1620 x 14.5 = 1022 v + 1620 V
23490 = 1022 v + 1620 V ..... (1)
Use the formula of coefficient of restitution
1 (14.5 - 0) = v - V
14.5 = v - V
V = v - 14.5 .... (2)
Put in equation (1)
23490 = 1022 v + 1620 (v - 14.5)
23490 = 1022 v + 1620 v - 23490
46980 = 2642 v
v = 17.8 m/s
Put in equation (2)
V = 17.8 - 14.5
V = 3.3 m/s
Thus, the speed of car is 17.8 m/s and the velocity of truck is 3.3 m/s after collision.
<h2>Answer: The half-life of beryllium-15 is 400 times greater than the half-life of beryllium-13.</h2>
Explanation:
The half-life of a radioactive isotope refers to its decay period, which is the average lifetime of an atom before it disintegrates.
In this case, we are given the half life of two elements:
beryllium-13:
beryllium-15:
As we can see, the half-life of beryllium-15 is greater than the half-life of beryllium-13, but how great?
We can find it out by the following expression:
Where is the amount we want to find:
Finally:
Therefore:
The half-life of beryllium-15 is <u>400 times greater than</u> the half-life of beryllium-13.