Physics - September 2007

"A man runs at speed v to catch the bus. At t=0, he is still a distance of 10m from the door when the bus starts to accelerate at a constant rate of 0.38 m/s^2. What is the minimum speed the man can run and still board the bus."

I know this involves a quadratic because I assume you have to use the equation [(xf) = (xi) + (vi)(t) + (0.5)(a)(t^2)], and that [b^2 - 4ac] (from under the root in solving a quadratic using the Q.F.) must equal zero in order to ensure that the man's speed is the minimum it can be so that he and the bus are in the same place at the same time... I'm just having difficulty setting up the problem properly.

Thanks in advance!

2007-09-18 12:49:06 · 2 answers · asked by Anonymous

what effect does this have on the velocity of the emerging bullet? Why do long range cannons have such long barrels?

2007-09-18 12:41:09 · 1 answers · asked by kntagler 1

2007-09-18 12:26:42 · 2 answers · asked by kimberlinus 1

A race car can be slowed with a constant acceleration of -11 m/s

A) If the car is going 55 m/s how many meters will it take to stop?

B) How many meters will it take to stop a car going twice as fast?


I don't understand how you can do this problem when they only give you one piece of information.

I'm not trying to get someone to do my homework for me, I just really don't know where to begin, I've never been good in applying math to science.

2007-09-18 12:24:19 · 1 answers · asked by Katie E 2

An apple falls straight down from an apple tree growing on a 20 degree slope. The apple falls a distance of 2.5m before hitting the ground. (A) What is the apples speed as it hits the ground? (B) What are the components parallel and perpendicular to the ground of the velocity?

2007-09-18 12:10:11 · 2 answers · asked by Anonymous

A car moves at 12 m/s and coasts up a hill with uniform acceleration of -1.6 m/s^2. How far has the car traveled after 6.0 s?

Soo I'm trying to decide what equation to use... D=VT?
I'm not sure if the 12 m/s if velocity or speed.
Could someone show me how to do this please?

2007-09-18 12:03:37 · 3 answers · asked by Katie E 2

A child in danger of drowning in a river is being carried downstream by a current that has a speed of 2.70 km/h. The child is 0.600 km from shore and 0.800 km upstream of a boat landing when a rescue boat sets out.
(a) If the boat proceeds at its maximum speed of 20.0 km/h relative to the water, what heading relative to the current should the pilot take?
° relative to the direction of the current
(b) What angle does the boat velocity make with the current?
° relative to the direction of the current
(c) How long does it take the boat to reach the child?
s

2007-09-18 11:54:16 · 1 answers · asked by justin l 1

Joe is trying to pick up Ryan who is waiting directly across the river. Joe heads straight across the river in his kayak at a velocity of 5 kilometers per hour, but the river current flowing at 5.2 kilometers per hour pushes him downstream. The actual velocity of his kayak is 7.21 Km/h.

If it takes Joe 25.2 seconds to cross the river, how far downstream (in meters) does Ryan have to walk to get in the boat?

2007-09-18 11:46:03 · 1 answers · asked by Brian 4

160m below. how many seconds before the plane is directly overhead should the supplies be dropped?

2007-09-18 11:36:28 · 1 answers · asked by ? 1

calculate a) the distance the car coasts before it stops, b) the time it takes to stop

2007-09-18 11:32:01 · 1 answers · asked by ? 1

i need 2 know 4 science class!!!

2007-09-18 11:23:12 · 1 answers · asked by l♥ve143~♥~♥~♥ 2

does anyone know the answers to these?

Given a fundamental of 125 Hz which of the following set of frequencies (from the sound spectrum) will most likely add to a strong sense of musical pitch in the fundamental?
a. 200 Hz
b. 500 Hz
c. 400 Hz
d. 250 Hz

Given a fundamental of 125 Hz, which of the following set of frequencies (from the sound spectrum) will most likely detract from a strong sense of musical pitch in the fundamental?
a. 250 Hz
b. 500 Hz
c. 375 Hz
d. 200 Hz

2007-09-18 11:20:19 · 1 answers · asked by JoAnna 2

i am impaired when it comes to math..my teacher asked us to do these practice problems but i have no idea how to find the answer to these can someone help me figure it out??

1) a tuning fork has a frequency of 343 Hz. asecond tuning fork is struck and a student notices a beat frequency of 3 Hz. what are two possible values of the second tuning fork??

2) the middle "C" has a frequency of 256 Hz and a wavelength of 1.3 meters. how fast does this sound travel.

2007-09-18 11:15:03 · 1 answers · asked by molly 1

A 47g sample of a conducting material is all that is available. The resistivity of the material is measured to be 1.2x10^-7 Ohm-meter, and the density is 8.12g/cm^3. The material is to be shaped into a solid cylindrical wire that has a total resistance of 1.5 Ohms. What is the length required in meters?

2007-09-18 10:53:58 · 1 answers · asked by krstilyzed 1

A youngster bounces straight up and down on a trampoline. Suppose she quintuples her initial speed from 1.9 m/s to 9.5 m/s.

(a) By what factor does her time in the air increase?
-What is the intial speed (in seconds)?
-What is the speed (in seconds) after it quintuples?

(b) By what factor does her maximum height increase?
-What is the intial height (m)?
-What is the height (m) after the intial speed quintuples?


Thanks for the help i've been stuck on these questions for an hour now. How do you do these???? THANKS! :)

2007-09-18 10:45:21 · 3 answers · asked by Natlsn12009 1

Don't make me build one of these to check the answers!!!

http://s223.photobucket.com/albums/dd78/floodtl/?action=view¤t=Resistors.jpg

2007-09-18 10:24:37 · 4 answers · asked by Anonymous

To test the quality of a tennis ball, you drop it onto the floor from a height of 4m. It rebounds to a height of 2m. If the ball is in contact with the floor for 12ms, what is the magnitude of its average acceleration during that contact?

2007-09-18 09:57:05 · 1 answers · asked by sophia 2

are they volume and mass?

2007-09-18 09:42:56 · 4 answers · asked by demarestian 1

2007-09-18 09:38:09 · 4 answers · asked by Anonymous

A world class long jumper leaves the ground with a velocity 7 m/s at an angle 35 degrees above the horizontal.

How far is the jump?

I get 5.8 m ...is that right?

2007-09-18 09:26:05 · 1 answers · asked by Captain Whiskerboy Litterbox 3

An elevator accelerates upward at 1.2 m/s/s. The acceleration of gravity is 9.8 m/s/s. What is the upward force exerted by the floor of the elevator on a 77 kg passenger? Answer in units of N.

If the same elevator accelerates downwards with an acceleration of 1.2 m/s/s, what is the upward force exerted by the elevator floor on the passenger? Answer in units of N,

2007-09-18 09:25:10 · 2 answers · asked by josh j 1

A ball rolls horizontally off the edge of a tabletop that is 1.11 m high. It strikes the floor 2.80 m away from the edge of the table. What is the initial (horizontal) velocity of the ball?

2007-09-18 09:17:35 · 3 answers · asked by jim m 3

here is my physics problem. this is all the information i have been given and i really have no clue how i can use it to solve the problem.... In an egg-dropping contest, a student encases an 85g egg in a styrofoam block. If the force on the egg is not to exceed 1.5N , and if the block hits the ground at 1.2m/s, by how much must the styrofoam crush?

any help would be GREATLY appreciated!

2007-09-18 09:17:13 · 2 answers · asked by Anonymous

A dolly and its wheels have negligible mass.
The object on the dolly weighs 304 N and
the force on the rope is 23 N. The
acceleration of gravity is 9.8 m/s/s.

If a person pulls on the rope with a
constant force what is the
acceleration of the system? Answer in
units of m/s/s.

How far will it move in 3.29 s?
Answer in units of m.

2007-09-18 09:15:06 · 1 answers · asked by josh j 1

2007-09-18 09:08:39 · 3 answers · asked by Anonymous

A ball is thrown vertically upward with a velocity of +13.0 m/s.

(a) How high does it rise?

(b) How long does it take to reach its highest point?

(c) How long does the ball take to hit the ground after it reaches its highest point?

(d) What is its velocity when it returns to the level from which it started?

2007-09-18 09:03:02 · 1 answers · asked by Foxychick 1

Here is the problem-- A glider is moving a velocity vector Vg = 40m/s i - 24 m/s j when it enters the wind current Vw that blows due south with a constant speed of 20 m/s.

1) What is the i/j equation of Vw

2) What is the i/j equation for the gliders resultant velocity, and in what quadrant is the gliders velocity vector

3)What is the magnitude of the gliders new velocity vector

4) In what direction (in degrees) does the glider now head

5) What is the new azimuth of the glider

Ok, now i am completely lost and i have no CLUE what to do. I am not asking for the answers but an explanation of how to do each problem. Thanks

2007-09-18 08:57:35 · 1 answers · asked by Anonymous

Say a horse canters away from it's trainer in a straight line, moving 130.0 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.80 s. Use "away from the trainer" as the positive direction.
a] what is the average speed?
b] what is the average velocity?

I can't fully grasp the concept of the two, and also displacement...

2007-09-18 08:01:55 · 4 answers · asked by CL 1

If it's possible to superheat water, why not superheat superconductors? If transiton to normal state does not occur, they will remain superconductive, right?

2007-09-18 07:05:47 · 2 answers · asked by Alexander 6

say you're at ground level during an earthquake vs. on a mountain. is the shock greater, lower, the same?

2007-09-18 06:35:11 · 5 answers · asked by halimi022 1