Physics - September 2007

A small source of light "S" is located at a distance "L" from a vertical wall. An opaque object with a height of "h" moves toward the wall with constant velocity " v(arrow) " of magnitude "v" . At time t=0 , the object is located at the source "S" .

Find an expression for v(s), the magnitude of the velocity v(s)(arrow) of the top of the object's shadow, at time t .
Express the speed of the top of the object's shadow in terms of t ,v ,L, and h

2007-09-16 11:56:15 · 1 answers · asked by Tommy 2

A rock climber throws a small first aid kit to another climber who is higher up the mountain. The initial velocity of the kit is 21 m/s at an angle of 55° above the horizontal. At the instant when the kit is caught, it is traveling horizontally, so its vertical speed is zero. What is the vertical height between the two climbers?

2007-09-16 11:55:46 · 1 answers · asked by Anonymous

supplies is ejected horizontally backward with a speed of 14 m/s relative to the helicopter. Ignoring air resistance, what is the horizontal distance between the package and the helicopter when the package hits the ground?

2007-09-16 11:50:42 · 4 answers · asked by billy w 1

Can someone please give me some example problems of two-dimensional trajectory?? They can range from easy to hard, but they need to be worked out step by step. I am asking this because i don't know how to do these kind of problems for my physics class. (my teacher doesn't teach us) so i have homework, and i don't know how to do it. but instead of me asking you people to do it for me, i need you to give me some examples. that way i will be able to do my homework on my own. thank you so much :)

2007-09-16 11:05:13 · 1 answers · asked by Anonymous

A major leaguer hits a baseball so that it leaves the bat at a speed of 38.0 m/s and at an angle of 36.9° above the horizontal. You can ignore air resistance. (Assume upward is positive.)

a)At what two times is the baseball at a height of 13.0 m above the point at which it left the bat?
first time ________s
second time_______s

b) Calculate the horizontal and vertical components of the baseball's velocity at each of the two times calculated in part (a).
first time
____m/s (horizontal)
____m/s (verticle)
Second Time
____m/s (horizontal)
_____m/s (verticle)
(c) What is the magnitude and direction of the baseball's velocity when it returns to the level at which it left the bat?
_____m/s
______ degree (below the horizontal)

2007-09-16 10:58:50 · 1 answers · asked by Anonymous

Two basketball players are essentially equal in all respects. (They are the same height, they jump with the same initial velocity, etc.) In particular, by jumping they can raise their centers of mass the same vertical distance, H (called their "vertical leap").
The first player, Arabella, wishes to shoot over the second player, Boris, and for this she needs to be as high above Boris as possible. Arabella jumps at time t=0 , and Boris jumps later, at time tR (his reaction time). Assume that Arabella has not yet reached her maximum height when Boris jumps.

1) Find the vertical displacement D(t)= hA(t) - hB(t) , as a function of time for the interval 0Express the vertical displacement in terms of H , g , t and .
D(t) = ?
2)Find the vertical displacement D(t) between the raised hands of the two players for the time period after Boris has jumped (t>tR) but before Arabella has landed.
Express your answer in terms of t, tR , g , and H.
D(t)=?

2007-09-16 10:57:22 · 1 answers · asked by mandy 1

A small source of light S is located at a distance L from a vertical wall. An opaque object with a height of h moves toward the wall with constant velocity of magnitude v. At time t=0, the object is located at the source S.

2007-09-16 10:51:28 · 1 answers · asked by mandy 1

A car with a velocity of 25m/s [E] changes it's velocity to 25m/s [S] in 15sec. Calculate the car's average acceleration.
um, i just want to know do i have to change one of 25m/s to minus sign?? and the answer for this question is 2.4m/s^2 [45 degerees S of W] thx :)

2007-09-16 10:34:14 · 1 answers · asked by Anonymous

vertical spring of constant, 19.6 N/m - (A) determine the maximum compression of the spring. (B) what is the answer to part A, if the putty is dropped onto the spring from a height of .500 m from the top of the spring?

I need step by step instructions on how the answer for B is done. I have part A just need help step wise to resolve B.

2007-09-16 09:45:30 · 1 answers · asked by JustMe1962 3

Are microwaves dangerous. If so, how?
Is it the light that can cause cancer or somthing? Or anything other dangers?

Also do they have any medical uses?

2007-09-16 09:44:11 · 11 answers · asked by Anonymous

A ball bearing rolls backwards and forwards on the vertical track shown in the diagram:
http://i14.photobucket.com/albums/a348/Drakhys-2/slope4a.gif
It always starts to roll from the top of the track, either at the left or at the right. The shadow of the ball is seen on the horizontal ground beneath the track, and the position of the shadow is measured along the ground, with the origin at the bottom of the track at point O. The four statements below concern the motion of the shadow. Identify whether each is true or false.


1. For motion from right to left, the velocity and the acceleration at the point B are both negative.
2. For motion from left to right, the position and the acceleration at point B are both negative.
3. For motion from left to right, the position and the velocity at the point A have opposite signs.
4. For motion from right to left, the position and the velocity at point A are both negative.

I said: F, T, F, T. Is this correct. If not, why?

2007-09-16 09:39:30 · 2 answers · asked by Bikki 3

What is true about the direction of the electric field just outside the surface of a conductor?

2007-09-16 08:33:05 · 4 answers · asked by Anonymous

A mass m is attached on a horizontal spring and is immobile.The k of the spring is 2000 N/m.We move the mass away from the equillibrium point to an amplitude A'=0.16 cm and then we set it free to move.It does a damped oscillation, with an amplitude which is getting smaller 25% in evey oscillation.

Find how much will the total energy be decreased after the two first oscillations of the mass.

2007-09-16 08:04:45 · 1 answers · asked by Joey 1

Thanks to a Yahoo Physcis expert they gave me the following:

´h=-16*t^2 +70 feet
v=-32 *t feet/s
h=0 t^2 = 70/16 so t =sqrt(70/16)=2.09 s

Can I get the answer too for each calculation? Just want to double check what I am doing is right

2007-09-16 07:31:22 · 2 answers · asked by Cutekow 2

2007-09-16 07:11:48 · 4 answers · asked by ♥♥♥♥ 4

I you dropped a ball from a 70 feet, how do I calculate the velocity of the ball? How about a calculation for how long it is in the air before it hits ground? And lastly determining a function for the height of the ball t seconds after it's released? Sorry but thanks, this is a tough one........

2007-09-16 07:11:01 · 3 answers · asked by Cutekow 2

2007-09-16 07:02:49 · 4 answers · asked by Anonymous

I need something fun and hands on that has something to do with physics, maybe even something that isn't the old static electricity or magnets demonstration. Someone mentioned to me paper airplanes but i was thinking of maybe bubbles or something. Any help would be very much appreciated.

2007-09-16 06:58:59 · 2 answers · asked by Voldemort 2

Okay, i'm completely lost on this question. As much as I know, is that on a 2-d plane, you can find the X and Y component using sin, and cos. Then find the length of the vector using pathagrean theorem. However right now I have a questions saying:

"A ferryboat transports tourists among three islands. It sails from the first island to the second island, 4.94 km away, in a direction 37.0° north of east. It then sails from the second island to the third island in a direction 57.0° west of north. Finally, it returns to the first island, sailing in a direction 28.0° east of south."

But i'm completely lost with how to start it.

2007-09-16 06:56:43 · 1 answers · asked by phrozenwarrior 3

Draw a diagram showing vectors a and b and the resultant.

2007-09-16 06:46:15 · 1 answers · asked by Anonymous

a stone is thrown upward from the top of a building at 25 degree angle to the horizontal with an initial speed of 15 m/s. if the stone was in the air (free falling?) for 3s how tall is the building?

2007-09-16 06:44:06 · 1 answers · asked by Captain Whiskerboy Litterbox 3

2007-09-16 06:43:58 · 1 answers · asked by Anonymous

Hello everyone,

Given that wood chips float on top of lakes (correct me if I'm wrong, I haven't been near one in awhile), how do you measure the volume of wood chips without using volume displacement? Can you measure it, or is that just too unreliable since wood chips come in a bunch of dimensions?

2007-09-16 06:42:25 · 2 answers · asked by Oompaloompa 2

A ball is rolled up a long, sloping driveway with an initial velocity of 5 m/s. The absolute value of the ball's acceleration is 3 m/s2. Assume the ball's initial position is zero and the uphill direction is positive.

Find the ball's position (in m) every second from t = 0 to t = 6 s.

2007-09-16 06:41:34 · 2 answers · asked by Anonymous

A ball is thrown vertically upward (assumed to be the positive direction) with a speed of 20.0 m/s from a height of 4.0 m.
(a) How high does the ball rise from its original position?
m
(b) How long does it take to reach its highest point?
s
(c) How long does the ball take to hit the ground after it reaches its highest point?
s
(d) What is the ball's velocity when it returns to the level from which it started?
m/s
show how you did it thanks

2007-09-16 06:38:45 · 1 answers · asked by Anonymous

2007-09-16 06:38:36 · 1 answers · asked by fishead 1

A baseball was clocked at 100.8 mi/h. If a pitch were thrown horizontally with this velocity, how far would the ball fall vertically by the time it reached home plate of 60 ft away?

2007-09-16 06:38:34 · 1 answers · asked by Captain Whiskerboy Litterbox 3

A ball thrown vertically upward is caught by the thrower after 9.1 s.
(a) Find the initial velocity of the ball.
m/s (upward)
(b) Find the maximum height it reaches.
m

Can you show me how you get the answer because i dont know how you calculate displacement when a ball is thrown upward.

2007-09-16 06:37:41 · 1 answers · asked by Anonymous

2007-09-16 06:37:18 · 2 answers · asked by ? 1

help

2007-09-16 06:12:20 · 3 answers · asked by Anonymous