Hai guys, I need help with homework again. Below, I have a picture of my physics homework, and I need help with numbers 6-10. I definitely don't understand #6, and I don't really know what to do when there are waits in between the distances or whatever (#7). Any help is appreciated!



I really should make a "Dem0n's Homework Help Club." >_>

If you don't understand question 6, you need to look at the definitions of velocity and speed and how they're related to distance, displacement, and time.

velocity = displacement/time
speed = distance/time

On question 7, and for problems like it, you need to figure out how long she was traveling at a constant velocity for in order for 20 minutes of 0 velocity to bring the average down to the given number. Think about it this way: If she travels for 20 minutes--the same amount of time she rests for--what would her average speed over the entire interval be? If she travels for 40 minutes? Find the relationship.

For #9, let's say we have 4 variables, v₁, v₂, t₁, and t₂.
v₁ = Velocity of turtle = 10.0 cm/s.
v₂ = Velocity of hare = 20*v₁ = 200 cm/s or 2.0*10²
t₁ = The total amount of time the turtle ran in seconds.
t₂ = The total amount of time the hare ran = t₁ - 120 (secs)
d = The total length of the race in centimeters.

Because by the end of the race, the turtle won by 20.0 cm, we have the equation v₁ * t₁ + 20.0 = v₂ * t₂. Substitute out the variables, solve for t₁. That's the answer for #9 in seconds. For #10, substitute and solve d = v₁ * t₁.

For #6, I don't know whether the 5 mins taken to find the wallet count, so I'm assuming they don't.
a. v = d/Δt = 40.0 km / (60.0 - 0.0) minutes.
b. s = (d[sub]1 + d[sub]2 + d[sub]3)/Δt = (20.0 + 20.0 + 40.0) km / (60.0 - 0.0) minutes.

Post has been edited 1 time(s), last time on Sep 20 2011, 2:26 am by Raitaki.

Why would they mention it if it didn't? It's a physics problem.

#7:
v[sub]1 = Velocity, 22 mins rest not included = 89.5 km/h
v = Average velocity = 77.8 km/h
t = Total time taken (hours)
22.0 minutes = 11/30 hours
v[sub]1 * (t - 11/30) = tv. Solve for t.
#8:
v = Velocity = 6.50 m/s
t = Time taken to reach ground = 34.0 seconds
d = Displacement (meters)
vt = d. Solve for d.

Quit answering the problems for him.

Go read your physics book.

4srs, Raichu, I at least tried to be a good teacher >.>

It's futile unless you went ahead and reteach him pre alg and alg 1.

This is the most helpful answer you can get. Everyone learns by working it out themselves. If your teacher isn't doing a good enough job, then you need to force yourself to sit down with your physics book, read through the section, and work the problems out yourself.

If you don't have the answers to the questions you're doing, then start with question in the book or online where the answers will be available, and then you can try it yourself and figure out how to arrive at the right answer.

This is so cute.

Well, I'm way too tired to even copy down the shit raitaki gave me. Oh well. I had those formulas in my notebook, but I didn't even think about looking at them. I don't understand, at all, how you solve this stuff when you incorporate time spent not doing anything.

Do yourself a favor, throw away your formulas. You don't get to use them until you understand them.

Both velocity and speed are about distance traveled/displacement vs. time that has passed since the object started moving, so you can think of the wasted time as periods at which s and v = 0.

But textbooks are so bad at teaching concepts.
Go watch a youtube video about it.

Quote from Sacrieur

Do yourself a favor, throw away your formulas. You don't get to use them until you understand them.

Quote from Sacrieur

Quit answering the problems for him.

Go read your physics book.

These.
Demon, you seriously need to rethink your classes if you can't understand how to solve distance/time/velocity (or speed) equations when given two of the three pieces. Homework help should be given only when the person actually understands the problem in question.

Quote from name:K_A

Quote from Sacrieur

Quit answering the problems for him.
Go read your physics book.

But textbooks are so bad at teaching concepts.

That's what teachers and studying are for. He's doing baby physics, and he needs help? You can't let him suckle on your tit forever, mother hen.

I need help when I haven't been taught anything and am just given work to do. Even if its the basics, if I haven't been taught anything, I'm not going to understand it.

You can't even use a formula?
Hint:
Kilometers per hour = k/h
Meters per second = (k*1000)/(h*3600)'
You should have learned how to use these formulas in 8th grade.
I don't know all the formulas you need, but it's pretty simple math for most of it.

Most of the measurements used in physics and other science classes: (Energy, Weight, Volume, Speed, Veolocity, Density, Work) are just combinations and ratios of basic measurements: (Time, Distance, Mass, Temperature)

Post has been edited 2 time(s), last time on Sep 20 2011, 9:47 pm by K_A.

Ask your teacher to do his/her job.

My teacher is the most aloof and lawltastic person you'd ever meet. He'll be in the middle of a sentence, freeze for a few seconds, and then start talking about something. It's funny how he writes the exact same way too. There'll be a bunch of spaces between words and a whole bunch of typos. ololo