Question

Question 2 - 70 Marks A hydraulic car lift system is shown schematically in Figure 1. The system is being designed to lift a 1500 kg car via two pistons (driven pistons) located underneath the wheels of the car (distributing the weight of the car so that half is on each piston). The cylindrical pistons each have a diameter of 10cm. The hydraulic system will be driven by a person sitting (or standing) on the driving piston. The car weighs 1500 kg and the person weighs 85 kg. 1500 kg 85 kg 120 cm/s d 10 cm 10 cm Figure 1: Hydraulic car lift system Part (a) — 40 Marks What diameter should the driving piston have if we want the car to accelerate upwards at 20cm/s2 when the person is on the piston? Part (b) – 20 Marks What pressure difference will be measured by the gauge when the person loads the driving piston? (assuming any height differences are negligible) Part (c) - 10 Marks Does it matter (from a fluid mechanics point of view) what fluid is being used? What property of the fluid is important in this decision?

Answer 1

Ö'cof car) =) 20cm/see? 2) OY 0-2 m/sec? me=) 1500 kg Car 10.2 online > mg Force { Force Force - mg - ma > ma Force = mg+ma 1500 (9.8) +0.2) Force = 15015 This will be shared by two ati pistons. 15015=2Fp FP= 15015 FP = 75075 N Pressure in & lach Piston a Fe Area 750705 2 4 (2 xã)

sames as Pressure in any Cylinder This will be same perssure in man's piston 7507.5 85*9.81 7 Cloxiage # (Oxiz 7507.5 85x908) (10%) D.2 D,²= 10 x85x9.8) 7507.5 ID = 3.332 cm (b Dressure difference measured (۱اليا 7507.5 (loxial) =) 1955884.5 pa gauge Pressure ® No any fluid can be used untill it behaves as a fluid. "Po It works under Dascals law Pressure in fluid will distributed all over the fluid" IQ be equally a