Do you think this video is real or fake?
You can see the type of pressure washers he’s using here:
These are electric pressure washers with at max 2 gallons per minutes flow rate (7.57 litres). That means 16.69 pounds of water is coming out per minute (7.57 kg). That’s 0.556 lbs/second (0.25 kg) because there are 2 pressure washers – one for each hand.
So, do you think the video is real?
Hmm, I’m not sure… Let’s do the math:
First we need to understand what is going on. Newton’s Third Law tells us “for every action there is an equal and opposite reaction.” The water hitting the ground results in an equal force pushing the man upwards.
Here’s a little drawing to show the same concept with a water jet pack:
Notice how much bigger the water streams are in the water jet pack? It’s to allow for the huge water mass flow rate required.
Now back to the pressure washer jet pack.
Let’s assume these facts:
- 0.096″ nozzle oriface
- 2.0 GPM
- 2,000 PSI
Doing the calcs for:
Force = Change in Momentum of the Water Over Time
You find out that the 2 pressure washers used in the video could at best provide 15.4 pounds of force upwards.
The video is clearly a hoax with some fine editing.
However, note that if you spent $40,000 on a gigantic 20 GPM pressure washer that might just accomplish the task as it would provide around 160 pounds of upward force if you had 2.
Calcs in detail:
- Velocity in ft/sec equals 2 gallons per minute divided by 60 seconds per minute * 231 cubic inches per gallon divided by (PI * Diameter/4) to account for the oriface size.
- Run the numbers and that gives 928 ft/sec.
- Times that velocity with the above calculated mass flow rate of 0.556 lbs/sec) and divide by 32 and you get around 16 pounds of force.