# phy

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(Q1)A gas occupies a certain volume at 27c.If it is heated at constant pressure, its volume is exactly doubled at a temperature of. (a)54c(b)219c(c)327c(d)600c (Q2)If the specific heat capacity of water initially is4.2000/kg/k and the difference in temperature of water between the top and bottom of a 210m high water fall is (g=10m/s2) (a)0.05c(b)0.5c(c)1.0c(d)4.2c

• phy - ,

[Q1]
Note that for an ideal gas, the volume of the gas is directly proportional to the temperature of the gas (Charles' Law). Just think of it as when you have a balloon of certain volume, and then you heated it (temperature increases), the balloon will expand (volume also increases). NOTE that the temperature must always be in Kelvin units. In the question, the volume is doubled when the temperature is increased; therefore, the temperature is also doubled. We first convert the 27 C to Kelvin (just add 273):
27 + 273 = 300 K.
Then double it:
300 * 2 = 600 K (new temperature)
Since the choices are in Celsius, we convert it to Celsius:
600 - 273 = 327 C

hope this helps~ :)

• phy - ,

Q1
p₁V₁/T₁=p₂V₂/T₂
p₁=p₂
V₁/T₁=V₂/T₂
T₁=27℃= 300K
T₂=V₂T₁/V₂ =2 T₁= 600K =327 ℃

Q2
mgh=mcΔT
ΔT= gh/c=10•210/4200 =0.5℃