Latihan Termodinamika

TUGAS I TERMODINAMIKA I 3

1)Consider a river flowing toward a lake at an average velocity of 3 m/s at a rate of 500 m /s at a location 90m above the lake surface.Determine the total mechanical energy of the river water per unit mass and the power generation potensial of the entire river at the location. Jawaban Dik

:

: V=3 m/s

3

Þ=1000 kg/m

Ṽ=500 m3/s h=90 m Dit

:a)Em per unit massa b)Em

a)Em per unit massa

Þ= 3

1000 kg/m = m=500.000 kg Em=Ek + Ep 2

Em= mV + mgh 2

2

=0.5x500.000kgx(3m/s) +500.000kgx10 m/s x90m =2.250.000 J + 450.000.000 450.000.000 J =452.250.000 J =452.250 KJ

Em per unit massa= = =904,5 J/kg b)Em seluruhny=452.250 KJ 2)Determine the power required for a 2000kg car to climb a 100m long uphill road with slope of  0

30 from horizontal in 10s. a) At constantly velocity b) From rest to final velocity at 30m/s and c) From 35m/s to a final velocity 5m/s Disregard friction,air drag,and rolling resistance. Jawaban Dik

:

∆t=10s

:m=2000 kg s=100 m

Dit

:a)W pada kecepatan konstan

c)W pada kecepatan 35 m/s

b)W pada kecepatan 30 m/s 2

2

2

2

a)Wa= m(V1 -V2 )= x2000x(10 -0 )=100.000 J=100KJ

Ŵa=

=

=10 KW 2

2

2

2

b) Wa= m(V1 -V2 )= x2000x(30 -0 )=900.000 J=900KJ

Ŵa=

=

=90KW 2

2

2

2

c)Wa= m(V1 -V2 )= x2000x((-5) -(35) )=1000(1250)=1.250.000J=1250KJ

Ŵa=

=

=125KW

3)A damaged 1200 kg car is being towed by a truck.Neglecting the friction,air drag and rolling resistance,determine the extra power required a) For constant velocity on a level road o

b) For constant velocity of 50km/h on a 30 (from horizontal) uphill road and c) To accelerate on level road from stop 90km/h in 12s Jawaban

:

Dik

:m=1200kg ∆t=12s

Dit

:a)W untuk kecepatan konstan b)W dengan V=50km/h c)W pada kecepatan 90km/h 2

2

b) Wa= m(V1 -V2 )= x1200x(

Ŵa=

= 2

=

2

=9,645 KW 2

c)Wa= m(V1 -V2 )= x1200x(

Ŵa=

2

) -(0) =115.740J

=31,25 KW

2

2

) -(0) =375.000J=375KJ