Physics - September 2007

2007-09-12 07:20:06 · 2 answers · asked by Anonymous

2007-09-12 07:14:10 · 5 answers · asked by chimsy 2

i understand that is acceleration is the change in velocity over time. where i am getting confused is with deceleration vs. acceleration in a negative motion...how do you tell them apart on a graph?
for example, say i am going to jump in the air. i realize that from the moment i leave the ground, my acceleration will be equal to my gravity...but, what happens with my acceleration as i bend my knees down and then on my upward movement before i leave the floor...any help will be appreciated...i can't seem to get my head around this.

2007-09-12 07:11:43 · 2 answers · asked by meego99 2

Mass cannot be created or destroyed. This being said, with all that humanity has built and made, we have only changed matter. The only ways I can conceive of our Earth increasing in mass is from meteorites & energy from the sun. Perhaps my real question is, does the energy from the sun add to the mass of our planet and does anyone know approximately by how much?

2007-09-12 07:09:28 · 4 answers · asked by scottnra 2

Throw a single photon at a wall. Where it hits is its location at that exact moment. We also know that light travels at c (about 300k km/s). Therefore, we know both the speed and location of that photon.

2007-09-12 07:04:19 · 4 answers · asked by Anonymous

the answer is 5x10 -4 (10 to the power of minus 4)

anyone please tell me how to do this?i'v just started physics so i'm kinda lost lol

2007-09-12 06:52:42 · 3 answers · asked by GRAND SLAM 09 BABYYY 2

A stone is thrown straight upwards with an initial speed of 47.5 m/s. (a) How long is the stone in the air before it hits the ground? (b) How high does it rise? It is assumed that the stone heads upwards from ground level.

I got:

(a) 9.7 sec

(b) 115.2 m

Am I correct? I hope I used the right number for acceleration (-9.8m/s^2). Thanks.

2007-09-12 06:51:05 · 2 answers · asked by labelapark 6

An arrow shot straight upwards reaches a maximum height of 104.0 m from the bow. (a) At what original speed in m/s does it leave the bow and (b) how long in seconds is the arrow in flight until it returns to the ground?

My answers came out to:

(a) 45.1 m/s

(b) 4.59 s. Or, should this be 4.59s * 2?

Thanks.

2007-09-12 06:46:04 · 3 answers · asked by labelapark 6

A camera falls from a balloon, hitting the ground at a speed of 223.0 m/s. While ignoring air resistance, what is the (a) height above the ground in meters from which the camera was dropped and (b) the time in seconds it took for the camera to fall.

My answers came out to:

(a) 2.538 x 10^3 m

(b) 22.76 s

Is this correct? Thanks.

2007-09-12 06:37:41 · 3 answers · asked by labelapark 6

If your dog dies and in the future you make a time machine to go back in time to save him, will it work? Of course not, if you in fact made a time machine to save your dog, and were successfull in your attempt then why would your past self need to make a time machine to go back in the first place? Does anyone know of any good books that talk about the theories of paradox? I love the concepts of time travel and paradox together and am looking for a good read.

2007-09-12 06:25:18 · 4 answers · asked by Marc B 2

How far from the step edge will the ball touch the lower surface?

http://tinypic.com/view.php?pic=5zpz4lt

2007-09-12 05:58:27 · 2 answers · asked by Alexander 6

Can the average velocity of a particle be zero over a given time interval if it is not zero over a shorter time? Explain.

2007-09-12 05:52:58 · 12 answers · asked by t_steckbeck 1

2007-09-12 05:44:16 · 2 answers · asked by astalavista 1

please answer in a language i might understand! ie. no posh science speak - im already confused enough with physics!

2007-09-12 05:11:08 · 8 answers · asked by nyima s 1

A 100kg bungee jumper jumps from a bridge 40m above a river. The bungee cord has an unstretched lenght of 18m and has a spring constant k = 200 N/m
a) How far above the river is he when the cord brings him to a stop?
b) What maximum force does the cord exert on him?

2007-09-12 05:09:18 · 3 answers · asked by Anonymous

In a local bar, a customer slides an empty beer mug down the counter for a refill. The bartender is momentarily distracted and does not see the mug, which slides off the counter and strikes the floor 0.60 m from the base of the counter. The height of the counter is 0.900 m.

(a) With what velocity did the mug leave the counter?

(b) What was the direction of the mug's velocity just before it hit the floor? (below the horizontal)

2007-09-12 05:03:55 · 3 answers · asked by surfing86 2

What would be the freezing point?

2007-09-12 04:58:02 · 2 answers · asked by Anonymous

2007-09-12 04:43:16 · 7 answers · asked by Alexander 6

if you were travelling in a car down a road. if theorhetically you had a ball floating in the car, would that ball move with the car, or hit the rear window.

this maybe stupid, but i honestly don't know.

2007-09-12 04:05:16 · 4 answers · asked by Anonymous

Railroad car A rolls at a certain speed and makes a perfectly elastic collision with car B of the same mass. After the collition, car A is observed to be at rest. How does the speed of the car B compare to the initial speed of car A.

Okay now even though your not expert in physics....please help

2007-09-12 04:03:02 · 4 answers · asked by Sawira 2

Suppose a ball of putty moving horizontally with 1 kg m/s of momentum collides and sticks to an identical ball of putty moving vertically with 1kg m/s of momentum. What is their combined momentum?? What is the total momentum of the balls of putty before and after the collision??.

Please.... ow please help :(

2007-09-12 03:48:45 · 2 answers · asked by Sawira 2

Find the resultant of these two vectors: 2.00 x 10^2 units due east and 4.00 x 10^2 units and 30.0 degrees north of west

I'm in a coorespondance course that does a horrible job explaining how to do this, so if anyone could help me out with this it would be greatly appreciated.

2007-09-12 03:31:21 · 4 answers · asked by Anonymous

Hey friends,just wanted to know what is the difference between "vapour"and "steam".
Please dont paste any links..

2007-09-12 03:28:38 · 6 answers · asked by Anonymous

1) Does a 9 year old John Titor exist today?
2) Is his controversial time travelling proved to be a hoax?
3) If he exists, does his 38 year old self from the year 2036 appear to see his 9 year old self today?

2007-09-12 03:08:56 · 3 answers · asked by Kyle J 6

2007-09-12 03:03:09 · 1 answers · asked by Anonymous

A heavy rainstorm dumps 1.0 cm of rain on a city 5 km wide and 8 km long in a 2-h period. How many metric tons (1 metric ton = 10^3 kg) of water fell on the city? [1 cm^3 of water has a mass of 1 gram = 10^-3 kg.]

Thats the actual question straight from the book. I have no ssense of direction on what to do. I know i have to convert some units of measurement but i have no clue?

2007-09-12 02:41:29 · 5 answers · asked by Anonymous

We regularly hear about objects that travel faster than the speed of light, but I've never heard anything about the speed of dark. Does darkness travel or is it just static ?

2007-09-11 22:43:11 · 15 answers · asked by Anonymous

A bath contains 100kg of water at60 dergee C. Holad and cold taps are then turned on to deliever 20kg per minute each at temperatures of 70 degree C and 10 degree C.Hw long will it be before the temperature in the bath has dropped to 45 degree C. ??????assume complete mixing of water n neglect heat losses.??????????????????

2007-09-11 22:30:59 · 3 answers · asked by iqnabeel 1

please answer asap.. tnx

2007-09-11 20:53:21 · 1 answers · asked by Anonymous

2007-09-11 20:40:35 · 8 answers · asked by aliah_natasya2003 1