Feeling rusty with Engineering Fundamentals?
Or worried about passing the FE or PE exam?

LEARNerds gets you back up to speed, by making Engineering Practice
a fun, motivating, ridiculously-simple part of your daily routine.

Every morning at 7AM (EST) we jumpstart your day with a daily Engineering Question,
similar to concepts found on the Fundamentals of Engineering Exam (FE) & Professional Engineering Exam (PE).

# Setting the Pulley Trigger

The diet coke mentos funnel pours out into a 2 lbs bucket that's attached to a rope that's wrapped around a pulley. You want to figure out how much force F is initially needed to keep the bucket in a stationary state (before the coke starts pouring in).

If the coefficient of friction between the rope and the pulley is 0.15, and the pulley diameter is 6 in, what's the minimum force F?

Part of the puzzle (of life) is uncovering implicit clues, while deciding what assumptions to make. So comment on any ambiguities you see so others can learn to spot them too!

# A Funneled Container of Coke

BOOM! Your cannon hits a target that cues mentos to drop into eight 2 Liter diet coke bottles.

The diet coke spills out into a funnel that fills up another container. You estimate that the mentos causes the liquid to flow out at a rate of 2.25 fl oz/sec for 5 sec each. A Google search tells you that the density of diet coke is 0.997 g/mL.

You ideally want the mentos to cause 5 lbs of diet coke to flow into a container for the next part of your Rube Goldberg machine.

With this system, is enough coke being funneled into the next part? Or do you need MORE MENTOS?

Part of the puzzle (of life) is uncovering implicit clues, while deciding what assumptions to make. So comment on any ambiguities you see so others can learn to spot them too!

# Fire the Cannon - Projectile Motion

You've setup your safety switch. Now to position the cannon!

You have a toy cannon wired up to the safety switch and loaded with a very special cargo. Your target is across the room.

The target has to be placed 28 meters away. You also know that the initial velocity out of the cannon is
20 m/s. Assume that both the cannon and the target are at the same height.

What angle from the horizontal does the cannon need to be at to make the shot into the target zone?

Part of the puzzle (of life) is uncovering implicit clues, while deciding what assumptions to make. So comment on any ambiguities you see so others can learn to spot them too!

# Make a Safety Switch

You and your best friend about to build the best Rube Goldberg machine ever. You don't want to set it off accidentally, so you two decide to build a two-man safety switch.

The two-man safety switch has two buttons which need to pressed at the same time in order to activate your machine. That's nuclear defense security!

You and your friend scrounge up some parts and get ready to build the switch. You are going to use 2 transistors, one for each button. The transistors will act as switches. When both of you close your transistor switch, the circuit should activate the cannon to start the machine!

If you don't remember how transistors work, you can always ask your friend. He reminds you that....

## Transistors Review

### Open Switch - Inactive

The current flows from the voltage source on the left to the ground on the right. When there is no signal to the middle wire of the transistor, it is an open switch and no current can get from the left side to the right.

### Closed Switch - Active

When there is a signal on the middle wire of the transistor, such as this pressed button here, then the current is able to move from the left side to the right side of the transistor, and flow through to ground.

Which of the circuits below should you and your friend build?

Part of the puzzle (of life) is uncovering implicit clues, while deciding what assumptions to make. So comment on any ambiguities you see so others can learn to spot them too!

# A Drill Without a Bit

If a tree falls in the woods and no one's around to hear it, does it make a sound?

Of course it makes a sound! Just because no one is there, doesn't mean it goes away...

No, it doesn't make a sound. If no one knows it's there, then it might as well not exist...

This question debates common notions of reality. It asks, if something is not perceived at all, then how can it be said to actually exist? Over centuries critical thinkers have debated this question. Classical science is built on the presumption that there exists an external reality. But others argue that there is no way to separate the "observer" from the "observed."

In relation, Torque is also a force that isn't always perceivable and thus can be somewhat unintuitive. For instance, if you add a bit to a drill it's easy to see torque in action. But without a bit, you can place your hand on the end of the drill and yet feel no force except that of friction. So our question for you is... if a drill spins and there is no bit in it, does it have a torque?