# Homework Help: Pressure problem

1. Jan 15, 2016

### Nanu Nana

1. The problem statement, all variables and given/known data
A car is put into a garage higher by a hydraulic lift. How large should be the surface on which the vehicle rest if you to lift a vehicle of 1000kg higher with overpressure of 1 atm?

2. Relevant equations

Pabsolue pressure = P atmos + P relative
P=F/A
F=m xa

3. The attempt at a solution
P absolute = 101325 Pa +101325 pa
1000kg x9.81 m/s^2 / (A) = 202650
1000kg x 9.81 =202650A
A= 1000x9.81 /202650
A=0.04840 m^2

But the answer should be 9,682.10-2 m 2

2. Jan 15, 2016

### Dr. Courtney

It's always a hint when your answer is off by very close to a factor of two.

3. Jan 15, 2016

### Nanu Nana

I don't understand

4. Jan 15, 2016

### J Hann

What would be the net force produced using a closed cylinder containing air at atmospheric pressure?

5. Jan 15, 2016

### haruspex

Is there a vacuum above the car and the platform it stands on?

6. Jan 17, 2016

### Nanu Nana

No there is no vacuum

7. Jan 17, 2016

### haruspex

Right. So what force have you overlooked?

8. Jan 17, 2016

### Nanu Nana

9. Jan 17, 2016

### Nanu Nana

Force of gravity?

10. Jan 17, 2016

### haruspex

What force is acting on the platform that would not act on it under a vacuum?