Answer:
B. Cathode Ray Tube
Explanation:
In 1897, British physicist J. J. Thomson showed that cathode rays were composed of a negatively charged particle, which was later named the electron.
I'm assuming your question refers to the train travels 81 km in 2 hours, as in that's the total distance covered versus the speed for those 2 hours, whereas the 90 km in 2 hours the second time around is the total distance not speed I would assume.
Now... if it was going 81 km for the first 2 hours and 90 km for the second 2 hours then the average speed would be the mean of these numbers, with that being 85.5 km. Though, I doubt that's your question.
With that said, 81 km covered by 2 hours and 90 km covered by 2 more hours. To acquire the km an hour average, we'll have to divide the distance by how many hours it traveled:
81 / 2 = 40.5
90 / 2 = 45
Meaning the train was going 40.5 km an hour for the first 2 hours and 45 km an hour for the second 2 hours. Now, to find the mean:
40.5 + 45 = 85.5 / 2 = 42.75
In-case you were wondering, the mean is the sum of all the numbers in a set, divided by the total amount of numbers in that set, take for instance:
3, 5, 9, 2, 1, 5. -> There are 6 numbers in this set.
3 + 5 + 9 + 2 + 1 + 5 = 25 -> 25 is the sum of these numbers.
25 / 6 = 4.2 (estimated) -> 4.2 is roughly the mean or average between the original set.
Anyhow, with that aside the average speed between this I would believe would be 42.75 km an hour. I hope that helps, have a great rest of your day! ^ ^
| | Ghostgate (Alter) | |
Answer:
Required answer = 2.7 x 10^16 MOLECULES
Explanation:
We know that
1 m = 100 cm
so 1 m^3 = (100 cm)^3 = 1000000 cm^3 = 1 x 10^6 cm3
as per question, 2.7*10^{10} molecules in 1 cm^3
so number of molecules in 1 m^3
Number of molecules = ( 2.7 x 10^10 molecules /1 cm^3 ) x ( 1 x 10^6 cm3 / 1 m3)
Number of molecules = 2.7 x 10^10 x 1 x 10^6 = 2.7 x 10^16 per m3
Required answer = 2.7 x 10^16 MOLECULES
Answer:
B. 2nmv
Explanation:
Pressure is force over area.
P = F / A
Force is mass times acceleration.
F = ma
Acceleration is change in velocity over change in time.
a = Δv / Δt
Therefore:
F = m Δv / Δt
P = m Δv / (A Δt)
The total mass is nm.
The change in velocity is Δv = v − (-v) = 2v.
A = 1 and Δt = 1.
Plugging in:
P = (nm) (2v) / (1 × 1)
P = 2nmv
