Mechanical Engineering Intern Interview Questions

Mechanical Engineering Intern at Medtronic was asked...

May 4, 2010

You are in a boat in a pool with a rock in your hand. You throw the rock into the pool. Does the water level rise, drop, or stay the same?

7 Answers

depends on how big the pool is and how accurately you can measure the water rise

you're already in the pool with the rock, so the water displaced is the same...this other guy is stupid

If the rock were neutrally buoyant the water level would remain the same. It is heavier than water which causes it to displace more than its own volume while in the boat compared to at the bottom of the lake. Therefore the water level of the lake would go down.

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Mechanical Engineer Intern at Nokia was asked...

Mar 9, 2012

If you have a refrigerator in an isolated room (no heat in or out) and left the door to the refrigerator open, what would happen to the temperature to the room? Would it go up, down or say the same?

11 Answers

If the door to the refrigerator is left open, the frige has to work harder because now it has to try to cool the entire room rather than just the inside of the frige. The coils and condenser in the back of the frige would create more heat thus heating the room up.

The temperature of the room would stay the same - the key is the fact that it is in an isolated room. There is no heat exchange between the room and it's external surroundings.

The refrigerator will warm up the room. If you look on the back of the refrigerator, you will see metal grating. Touch it. Its warm! A refrigerator is transporting heat from the inside cavity to the outside. However, the power cord running from the wall is pumping energy into the refrigerator/room. Energy is powering the refrigerator. It is also running an irreversible process, the energy dissipates out as heat and work (mostly heat), making the net temperature of the room increase.

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I propose the room remains constant - but for the following reason. The room is reported to be isolated. I denote that to be a cube with no walls, windows, doors, plumbing, OR conduit or an electrical box that would allow cable or air to move within or without the isolated cube. Logically, in that the fridge is not powered, it is not generating heat through the use of the motor, condenser or heat - exchange coils. Really, it doesn't matter what the answer is... you've just got to defend it logically. If the fridge were powered - but was an excessively large model (as you might find in a grocery store walk in) the room might cool. If it were a smaller unit - the motor would have to work overtime to try and keep it cool - thus heating the room. Just be creative! That's what they're looking for. Can you think on your feet.

Aa

The room's temperature will be exactly as the refrigerator's temperature. Heat will be absorbed by the grating metal on the back of the refrigerator, so no need to worry about where the heat that refrigerator produces go.

Majority of the answers here are wrong. A refrigerator is a heat pump that move thermal energy opposite to the direction of spontaneous heat flow by absorbing heat from a cold space and releasing it to a warmer one. There is some work required to move this thermal energy from Cold to Hot. If we assume that the amount of work used to move this energy is negligible, if you leave a refrigerator door open in an isolated room, the room temperature will stay the same. https://en.wikipedia.org/wiki/Heat_pump https://en.wikipedia.org/wiki/Refrigerator

If its an isolated room the frig will not be able to be plugged in to an outlet. So remains the same

The room temperature will remain the same. The reason for this lies in its basic principle of vapor compression cycle. Its true that refrigerator transfers the heat from one place to another. But one has to remember that the door is open. So, As heat is extracted by refrigerant and thrown in room using condenser and since the room is isolated and refrigerator door is open.. the same heat will be added inside refrigerator and same refrigeration cycle continues after that. In a way refrigerator is not able to cool anything. it is just continuously maintaining energy equivalence.

In this case, there is a net gain of energy from the refrigerator outlet into the room and no loss of energy out of the room. Thus, the room will warm up since there is a gain of energy.

Part of the room's temperature would decrease slightly. The other part of the room's temperature will stay the same. Since the refrigerator's energy is not large enough to cool the whole room it will cool a small portion of the room.

Mechanical Engineer Intern I at Valero Energy was asked...

Jul 10, 2014

We were sitting in the third floor of a 16 floor building. After asking me about my experiences with working within a group the interviewer suddenly asked me, "How many pennies would it take to stack as high as this building?"

2 Answers

Mechanical Engineering Intern at Woodward was asked...

Apr 2, 2014

If you had a ton of projects given to you that needed to be completed by the end of the week and there was no way for you to complete them all what would you do? (Was supposedly a trick question)

1 Answer

Mechanical Engineering Intern at Burns & McDonnell was asked...

Dec 4, 2012

There were some challenging questions, but they were aimed to give you a chance to answer them very well. I didn't feel that any of the questions were difficult to answer and was able to give a solid response to each question.

1 Answer

Mechanical Engineer Intern at LORD Corporation was asked...

Jul 14, 2013

No real difficult questions, just asked what I was interested in doing and a little about my past experience. (internship position, so it was relatively basic.) Asked a little about basic stress/strain curves.

1 Answer