# Search results

1. ### Gravitation (planetary motion)

Is it possible that your sketch is a misinterpretation of the problem description? If p is on the orbit, when the particle comes around to the location of p, the force would become infinite (with n being a negative exponent). I am assuming that r is the distance to p. And in that case, I can not...
2. ### Acceleration graph

In graphs of a thrown ball, assume that time starts when the ball leaves the hand. So would the acceleration of the throwing motion be part of the graph?
3. ### Acceleration graph

If you are confused by what is said in any of our posts, likely any of us that are connected could explain/reword the post for you. We don't explain how to get the answer, but if necessary we can explain posts that have come in for you.
4. ### Newton's Second Law — Net Force problem

I think your solution is equivalent to one of a list of perhaps 2 or 3 methods that would get full credit. One quibble about your worksheet: in one line you gave g as the unit where I think you knew, from how you converted the numerical part, is kg. That could cost you. There were several...

6. ### Why can we ignore certain circuit paths?

I found this to be an interesting discussion. I can not tell if the worry has been eliminated, so I would like to add my way of seeing that. Current would be flowing down the schematic thru R1. Let the potential of the "horizontal wire" be Vh. What if some current tried to continue going down...
7. ### Forces and vectors: pulling a baby buggy on soft ground

Where did the 64 come from? Certainly not the 64 N in frame #8. In which direction are you now trying to work out the total force -- total force exerted on the ground?
8. ### Kirchhoff's law problem with two batteries

Another approach: You know that the ammeter reading is to be zero. So assume that is the case and simplify your equations accordingly.
9. ### How is the moment at A using the Force 1200N calculated?

You are asked to find moment of this Force about point A. Don't assume the bracket is going to rotate to a new position. This would be an analysis of the twisting torque on the bracket (perhaps to see how strong the bracket needs to be considering what will be applied to it in use). Doc Al said...
10. ### Time it takes to swim across a river

I am back. I see that Orodruin caught me misreading the problem. He swims at 4 kph, so the minimum time to the opposite shore would be 540 s. So the book's 624.3 s may be right Edit: since the landing point is to be exactly opposite. Picture yourself at the bank of the river about to jump in...
11. ### Time it takes to swim across a river

I need to sign off for tonight. I hope someone else will take up monitoring and aiding your progress.
12. ### Time it takes to swim across a river

Doc Al said Doc Al's "at an angle" means not perpendicular. Your vertical and horizontal sides would be perpendicular, would they not?

14. ### Time it takes to swim across a river

Here is a nudge: Review Doc Al's post #8.
15. ### Time it takes to swim across a river

Yes, there is an error somewhere. Before we knew that the goal was to go straight across the river, I worked it out assuming all of his speed would be dedicated to getting across the river quickly. That would yield the minimum time considering his speed and width of the river. That time was 1080...
16. ### Time it takes to swim across a river

OK, please let us know if Doc Al's last post has helped you see how to make progress on this.
17. ### Time it takes to swim across a river

To clarify: when you say upwards, do you mean what I would call upstream (edit: or upriver)?
18. ### Falling Chicken

I recommend the advice in post #2. So that means to develop an expression for delta T in terms of m, g, h, and c.
19. ### Finding the depression and the tension of the string

Please explain your equation: You said in your original post that x is the hypotenuse. Perhaps you should draw the triangle of which x is the hypotenuse. Then explain what is lo, Δl, and y. Perhaps just draw it for yourself (if posting a photo would be a problem) and see if you do not see an...
20. ### Sliding on a water slide

Perhaps it should have said ?? That would mean the hypotenuse is sqrt(5^2 + 25^2) m.
21. ### Voltmeter problem from (OCR paper) multiple choice

Yes, the procedures done to go between the 2 views in the 2 cases are equivalent. In the first, the external resistor is added by throwing the switch, in the second, the external resistor is added by getting out the soldering iron (or similar method of connection).
22. ### What are the names of these "F" arrows in these three diagrams?

Another way to tell you verbally how to draw the resultant of Fx and Fy (top left fig): Imagine Fx and Fy being 2 sides of a rectangle. Now add the other 2 sides of the rectangle (each equal length and parallel to Fx and Fy). Now draw a vector that is a diagonal of the rectangle starting from...
23. ### Circuit Analysis Question -- Solving for a multi-resistor circuit

Your book's answers are wrong on this question!!! Your last post showed significant confusion caused by the error in your book saying what the answers to these 2 parts should be. I will show you how close you were and hopefully eliminate some confusion. In your initial post, you said . You...
24. ### Hard time with this Vector Velocity Problem

Another way to describe what needs to be done: The plane needs a heading such that its East-West component of its 200 km/hr cancels the wind's 85 km/hr.
25. ### What forces affect an astronaut?

a) In the frame of reference of the station -- which is in orbit around the Earth, if the astronaut is hovering in the middle of a cabin without hitting anything, how is that happening? b) From the point of view of a person on earth, the astronaut circles the Earth several times a day. How is...
26. ### Circuit Analysis Question -- Solving for a multi-resistor circuit

The answer in your book and the statement of the problem that you posted are not compatible. To be sure that you know how to solve those questions, please answer this: Just from the statement of the problem, what would your answers be?
27. ### Circuit Analysis Question -- Solving for a multi-resistor circuit

I should make certain that you know - that is the sum R1+R2. So what are the R1 and R2 values? About part b, do you have an answer? Since you understood that 3.75 ohms = 15v/4 amp, I expect that you can find an answer for the current thru R3+R4. Or does does the fact that R3 and R4 have...
28. ### Circuit Analysis Question -- Solving for a multi-resistor circuit

You said "I got 3.75 ohms (15v/4 amp)". I agree with you. There may be an error in the write-up of the problem or in what your book said the right answer should be. For (b), can you explain what the (11.9) means? That might be a clue. Can you ignore a for now and answer b?
29. ### Electricity in transmission lines (Simple V^2/R =P)

I was trying to steer you to a method of solving that I thought would demonstrate a more clear way to look at it: You could calculate the current using P = V*I. And then find the resistance, using as data the above current and the power that is lost to heat (P_lost=1% of P) while that current...
30. ### Electricity in transmission lines (Simple V^2/R =P)

The power lost via P = I^2*R heating is just 1% of the total power. Now, if you only knew the current ...