Answer
given,
gauge pressure = 1.94 x 10⁵ Pa
Pressure due to 4.90 m column of water
= ρ g h
= (4.90) x (1000) x (9.8) Pa
= 48020 Pa
Gauge pressure of second floor faucet
= 1.94 x 10⁵Pa - 48020 Pa
P_g= 145980 Pa
( b )
Let h = height of faucet from which no water can flow even if open
P = ρ g h
1.94 x 10⁵ = h x(1000) x (9.8)
h = 19.79 m
The air would contract therefore the answer is the second choice.
Answer: a) 274.34 nm; b) 1.74 eV c) 1.74 V
Explanation: In order to solve this problem we have to consider the energy balance for the photoelectric effect on tungsten:
h*ν = Ek+W ; where h is the Planck constant, ek the kinetic energy of electrons and W the work funcion of the metal catode.
In order to calculate the cutoff wavelength we have to consider that Ek=0
in this case h*ν=W
(h*c)/λ=4.52 eV
λ= (h*c)/4.52 eV
λ= (1240 eV*nm)/(4.52 eV)=274.34 nm
From this h*ν = Ek+W; we can calculate the kinetic energy for a radiation wavelength of 198 nm
then we have
(h*c)/(λ)-W= Ek
Ek=(1240 eV*nm)/(198 nm)-4.52 eV=1.74 eV
Finally, if we want to stop these electrons we have to applied a stop potental equal to 1.74 V . At this potential the photo-current drop to zero. This potential is lower to the catode, so this acts to slow down the ejected electrons from the catode.
Answer:
Cp= 0.44 J/g.C
This is heat capacity of metal.
Explanation:
From energy conservation
Heat lost by metal = Heat gain by water +Heat gain by calorimeter
Because here temperature of metal is high that is why it loose the heat.The temperature of water and calorimeter is low that is why they gain the heat.
final temperature is T= 30.5 C
We know that sensible heat transfer given as
Q= m Cp ΔT
m=Mass
Cp=Specific heat capacity
ΔT=Temperature difference
By putting the values
55 x Cp ( 99.5 - 30.5) = 40 x 4.184 ( 30.5- 21 ) + 10 x ( 30.5 - 21)
Cp ( 99 .5- 30.5) = 30.65
Cp= 0.44 J/g.C
This is heat capacity of metal.
Let N be the normal force that forces the person against the wall.
Then u N = m g is the frictional force supporting the person's weight
and N = m g / u
also, N = m v^2 / R is the normal force providing the centripetal acceleration
So, m g / u = m v^2 / R
v^2 = g R / u
since v = 2 pi R T
4 pi^2 R^2 T^2 = g R / u and T^2 = g / (4 u pi^2 R)
T = 1/ (2 pi) (g /(u R))^1/2 = .159 * (9.8 m/s^2 / (.521 * 4.4 m)) ^1/2
T = .68 / s
Do you see any thing wrong here?
T should have units of seconds not 1 / seconds
v should be 2 * pi * R / T where T is the time for 1 revolution
So you need to make that correction in the above formula for v.
