## Textbook solutions on video

Giancoli 7th Edition, Chapter 4, Problem 62

(1:36)

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### Giancoli 7th Edition, Chapter 19, Problem 16

Hi Agp2196, $R_1$ and $R_2$ can be recognized as in parallel since they have both ends connected by wires. The bottom ends are connected by a wire, and the top ends are also connected by a wire. This means current at the bottom, coming from the positive end of the battery, has a choice of $R_1$ or $R_2$, and when you see current being given this choice, you know the resistors are in parallel. Resistor labelled $R_3$ is in series since there are no other options but to go through $R_3$ in order to continue through the circuit.

Hope that helps,
Mr. Dychko

### Giancoli 7th Edition, Chapter 19, Problem 16

I don't understand why those two are parallel and one is a series?

### Giancoli 7th Edition, Chapter 3, Problem 17

Hi joeotilio25, thanks for your question. Gravity is a force, just like any other, and it's sign depends on how you've chosen to define your coordinate system. Traditionally, positive is chosen to be upwards, which makes any vector pointing downward, be it velocity, displacement, acceleration, or force, negative when pointing down. In that coordinate system, the force of gravity would be negative since it's pointing down. So, gravity is negative in a coordinate system where up is positive, and gravity is positive in a coordinate system where down is chosen to be positive.

Hope this helps,
Mr. Dychko

### Giancoli 7th Edition, Chapter 3, Problem 17

Hi.Sr. I would like to know when the gravity is positive or negative

### Giancoli 7th Edition, Chapter 20, Problem 33

Never mind, I missed that the wire is horizontal. Thanks