ES330
HW#2
Due 9/11/2025
1. (3 points) Draw the force distribution due to the hydrostatic gage pressure from the
water on the gate shown below.
water
Gate
2. (7 points) The public often sees cars
fly off a bridge into a body of water
during a car chase. While sitting around
with a group of friends someone says
“That’s nor realistic” after the person
trapped in the car struggles to open the
door. You think in the back of your mind
“I can calculate that!” You decided to
estimate how far the water can go up the
door before the door can no longer be
opened. In the scenario you are looking
at the car is sinking with the front end
pointed straight down. (Note, you wisely
decide to do this in the privacy of your
own room, not in front of your friends!)
(a) (5 points) How far up the door can
the water go before a person no
longer be able to open the door of their vehicle while the passenger compartment is
still filled with air.
(b) (2 points) Justify/explain your answer, including any assumptions that you need to
make in order to solve the problem. Given the assumption you made, describe “who”
your solution applies to.
This question is highly open-ended. One key skill to develop when you are learning how
to solve problems is to develop a “mental model” of the problem. For the physical set-up
this can (and probably should) start out as a simplistic “cartoon”. In this case we have “a
car” that is sinking vertically with the rear end first. We want to know how far “up” the
door the water can reach before a person can no longer open the door. “Up” depends on
orientation, so we orient our car correctly and draw on what we want to know/find.
ES330
HW#2
Due 9/11/2025
Start this problem with a sketch. Solve it in variable form first before you put any
numbers in. When you do this you are creating your model of the system. And that
solution is independent of many of the assumptions you need to make to get a “number”
answer for this problem. The next step is to……
……..make engineering assumptions to do that with this problem. Another important part
of engineering problem solving is to understand what the assumptions and simplifications
you made mean to the answer you come up with. There are no right or wrong choices for
many of the assumptions/simplifications you will need to make in this solution, but those
assumptions affect the meaning/message of your solution. What does your answer mean?
If this were real life, who would your solution apply to? (This is a key aspect of part b….)