(1)A given mass of gas at 302k is trapped in a tube of volume v.calculate the temperature of the gas when the volume is reduced to two-thirds of its original value by applying pressure twice the original value.(2)A electric pump whose efficiency is 76% raises water to a height of 15cm.if water is delivered at the rate of 460dm^3 per minutes,what is the power rating of the pump.(3)A fruit from a tree of mass 3kg is 6m above the ground.calculate the P.E of the fruit if it has fallen from the tree.(4)An object of mass 5okg is placed on an inclined plane at 30 degree to the horizontal.The height of the incline plane is 300cm and its length is 400cm.what work is done in moving the object down the plane.(take g=10m/s).(5)The length of a side of a metallic cube is 20 degree.Given that the linear expansivity of the metal is 4 x 10^5.find the volume of the cube at 120 degree cencius.PLEASE WITH WORKINGS O.THANK YOU

Im sorry, i dont know about it because im not a science student. I wish the mods pushes this educational piece to the front page. At least its better than the picture of tonto dikeh and her christmas goat!

well! 4 now i will answer questn 3. And will be back tomorrow 4 more.

Ans. 3:

Given;
mass m = 3kg,
height h = 6m, and
accel due to gravity, g = 9.8m/s
or 10m/s (g is a constant, which is often given in d question: unlike urs )
.

Potential Energy, PE
= m * g * h

= 3 * 9.8 * 6
= 176.40J

good night.

Number 4:

Solution: ( see sketch below for clearity)

Mass of object M = 50kg
Angle of inclination ¤ = 30˚
Length of plane S = 400cm
Hiegth of plane H = 300cm

Workdone W is the force required to move the object down the plane against gravity

W = F ₓ S
Where F = W cos ¤
And W = M x g
50 x 10
Therefore F = 50 x 10 cos 30

Workdone W = 50 x 10 cos 30 x 400
= 500 x 0.5 x 400
= 100 000J
= 100KJ

Somebody should check if this is right. Thanks

Number 5:

!Something is wrong here!!
What do you mean by "The length of a side of a metallic cube is 20 degree"

Length in DEGREE??

Cross check and come back plz

I don't understand question 1 either. I believe that's a test on General gas Equations. Since the gas should be at s.t.p I believe its the Volume we should be looking for here instead of the temperature? Right?

Cross check again plz

lovemeohlord: (1)A given mass of gas at 302k is trapped in a tube of volume v.calculate the temperature of the gas when the volume is reduced to two-thirds of its original value by applying pressure twice the original value.(2)A electric pump whose efficiency is 76% raises water to a height of 15cm.if water is delivered at the rate of 460dm^3 per minutes,what is the power rating of the pump.(3)A fruit from a tree of mass 3kg is 6m above the ground.calculate the P.E of the fruit if it has fallen from the tree.(4)An object of mass 5okg is placed on an inclined plane at 30 degree to the horizontal.The height of the incline plane is 300cm and its length is 400cm.what work is done in moving the object down the plane.(take g=10m/s).(5)The length of a side of a metallic cube is 20 degree.Given that the linear expansivity of the metal is 4 x 10^5.find the volume of the cube at 120 degree cencius.PLEASE WITH WORKINGS O.THANK YOU

No 1.
I think this should involve the Ideal gas equation. There is no mention of the gas being at S.T.P.

(P1 x V1)/T1 = (P2 x V2)/T2

T2 = (P2 x V2 x T1)/(P1 x V1)
P1 = ?
V1 = ?
T1 = 302K
V2 = V1 x (2/3)
P2 = 2 x P1

T2 = (2 x P1 x (2/3) x V2 x 302)/(P1 x V1)

cancelling out,

T2 = 4 x 302/3 = 402.6K.


No 2.

1dm^3 = 1000cm^3
460dm^3 = 460,000cm^3
density of water = 1g per cm^3
This means that 460,000cm^3 of water weighs 460,000 grams
mass flow rate M = 460,000grams per minute = 460kg/60seconds.
M = 7.667Kg/s.

Height h = 15cm = 0.15m.

g = 10m/s^2

Energy = work = mass x g x h
Power = Energy/time = Work/time = mass flow rate x g x h.
Power required to pump the water P = 7.667kg/s x 10m/s^2 x 0.15m
P = 11.5W.

Since the Pump is only 76% efficient,
The power rating of the pump = P/0.76 = 11.5/0.76 = 15.13W.

Q4, I may be wrong but in my experience, work is done (against gravity) when an object is moved up the plane and not down the plane. I do not believe you do any work down the plain except when friction is taken into account. If that's the case, then the coefficient of friction has to be given.

Q5. As stated by Mr. Sylvekzee, this question has a serious problem with units. I want to assume that the initial temperature of the cube is 20 degree (celsius, fahrenheits, kelvin ?). What is the length of a side of the cube?

For number 3,i think if the fruit has fallen from the tree(to the ground),the fruit will be 0cm above the ground and P.E=mgh will be m*g*0=0.

@Beretta92:You might be right but the problem is that it was never mentioned that the fruit had gotten to the ground. There is also the possibility that the question could be considering the P.E. at the particular instant at which the fruit just fell from the tree. I guess that's why the height was given in the question anyway.