Question 4 (continued)
4.2.2
To draw the shear force diagram, we calculate the shear force at critical points along the beam.
- FA=20 kN (down) at x=0
- RB=31.25 kN (up) at x=1 m
- UDL = 5 kN/m from x=1 m to x=6 m
- FC=30 kN (down) at x=6 m
- RD=73.75 kN (up) at x=7 m
- FE=30 kN (down) at x=8 m
Step 1: Calculate shear forces at key points.
- At x=0 (just after A): VA=−20 kN
- At x=1 m (just before B): VB,left=−20 kN
- At x=1 m (just after B): VB,right=−20kN+RB=−20+31.25=11.25 kN
- At x=6 m (just before C, end of UDL): VC,left=VB,right−(5kN/m×5m)=11.25−25=−13.75 kN
- At x=6 m (just after C): VC,right=VC,left−FC=−13.75−30=−43.75 kN
- At x=7 m (just before D): VD,left=−43.75 kN
- At x=7 m (just after D): VD,right=VD,left+RD=−43.75+73.75=30 kN
- At x=8 m (just before E): VE,left=30 kN
- At x=8 m (just after E): VE,right=VE,left−FE=30−30=0 kN
The shear force diagram starts at −20 kN at A, remains constant until B. At B, it jumps up to 11.25 kN. From B to C, it decreases linearly to −13.75 kN due to the UDL. At C, it drops to −43.75 kN. It remains constant until D. At D, it jumps up to 30 kN. It remains constant until E, where it drops to 0 kN.
Question 5
5.1
The unit pascal (Pa) is the SI unit of pressure, defined as one newton per square meter (1Pa=1N/m2).
5.2
Pascal's law states that a pressure change at any point in a confined incompressible fluid is transmitted undiminished throughout the fluid such that the same change occurs everywhere.
5.3
Given:
- Area of plunger (Ap) = 25% of ram area (Ar)
- Stroke of plunger (Lp) = 0.161 m
- Force applied to plunger (Fp) = 560 N
- Area of the ram piston (Ar) = 0.524m2
- Neglect ALL losses.
Step 1: Calculate the area of the plunger.
Ap=0.25×Ar=0.25×0.524m2=0.131m2
5.3.1
Step 2: Calculate the volume of liquid displaced by the plunger in 12 pump strokes.
Volume per stroke:
Vstroke=Ap×Lp=0.131m2×0.161m=0.021091m3
Total volume for 12 strokes:
Vtotal=Vstroke×12=0.021091m3×12=0.253092m3
The volume of liquid displaced by the plunger in 12 pump strokes is 0.253m3.
5.3.2
Step 1: Apply the principle of conservation of volume.
Volume displaced by plunger = Volume moved by ram piston
Ap×Lp=Ar×Lr
0.021091m3=0.524m2×Lr
Step 2: Calculate the distance moved by the ram piston (Lr).
Lr=0.524m20.021091m3≈0.04025m
Step 3: Convert to mm.
Lr=0.04025m×1000mm/m=40.25mm
The distance moved by the ram piston in 1 pump stroke is 40.25mm.
5.3.3
Step 1: Calculate the force exerted by the ram piston (Fr).
According to Pascal's law, the pressure is constant throughout the fluid:
P=ApFp=ArFr
Fr=Fp×ApAr=560N×0.131m20.524m2=560N×4=2240N
The force exerted by the ram piston is 2240N.
5.3.4
Step 1: Calculate the mechanical advantage (MA).
MA=ForceonplungerForceonram=FpFr=560N2240N=4
The mechanical advantage of the press is 4.
5.3.5
Step 1: Calculate the fluid pressure in the liquid.
P=ApFp=0.131m2560N≈4274.81Pa
The fluid pressure in the liquid is 4274.81Pa.
5.4
Given:
- Number of cylinders = 3
- Plunger diameter d=171mm=0.171 m
- Stroke length L=300mm=0.300 m
- Speed N=230 r/min
- Slip = 16%
Step 1: Calculate the area of one plunger.
A=4πd2=4π(0.171m)2≈0.02294m2
Step 2: Calculate the theoretical volume displaced per minute for one cylinder.
Vtheoretical,1cyl=A×L×N=0.02294m2×0.300m×230r/min≈1.58286m3/min
Step 3: Calculate the theoretical volume displaced per minute for 3 cylinders.
Vtheoretical,3cyl=3×Vtheoretical,1cyl=3×1.58286m3/min≈4.74858m3/min
Step 4: Account for slip.
Actual volume delivered = Theoretical volume ×(1−slip)
Vactual=4.74858m3/min×(1−0.16)=4.74858m3/min×0.84≈3.9888m3/min
Step 5: Convert to litres per minute.
Vactual=3.9888m3/min×1000litres/m3≈3988.8litres/min
The volume of water delivered is 3988.8litres/minute.
Question 6
6.1
The Kelvin scale is an absolute temperature scale where 0 K represents absolute zero, the theoretical point of no molecular motion. The Celsius scale is a relative temperature scale where 0 °C is the freezing point of water and 100 °C is its boiling point. A 1-degree change in Celsius is equivalent to a 1-Kelvin change, but their zero points differ by 273.15 (0K=−273.15 °C).
6.2
Given:
- Surface temperature T1=27°C=300.15 K
- Surface pressure P1=101.325kPa=101325 Pa
- Bottom temperature T2=10°C=283.15 K
- Diameter of bubble at bottom d2=16mm=0.016 m
- Diameter of bubble at surface d1=42mm=0.042 m
- Density of water ρ=1000kg/m3
Step 1: Calculate the volume of the bubble at the surface (V1).
Radius at surface r1=d1/2=0.042m/2=0.021 m
V1=34πr13=34π(0.021m)3≈3.879×10−5m3
Step 2: Calculate the volume of the bubble at the bottom (V2).
Radius at bottom r2=d2/2=0.016m/2=0.008 m
V2=34πr23=34π(0.008m)3≈2.145×10−6m3
Step 3: Apply the combined gas law to find the pressure at the bottom (P2).
T1P1V1=T2P2V2
P2=P1V2V1T1T2
P2=101325Pa×2.145×10−6m33.879×10−5m3×300.15K283.15K
P2≈101325Pa×18.0848×0.9433≈1730000Pa
Step 4: Calculate the depth of the ocean (h) using the hydrostatic pressure formula.
P2=P1+ρgh
h=ρgP2−P1
h=1000kg/m3×9.8m/s21730000Pa−101325Pa
h=9800N/m31628675Pa≈166.19m
The depth of the ocean is 166.19m.
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