Physics - February 2007

if u were in a free falling elevator, is it possible to save your life by jumping up at the very second it hits the ground?

2007-02-25 11:36:27 · 4 answers · asked by willow 3

2007-02-25 11:36:06 · 3 answers · asked by Connie L 1

Can a scalar quantity be negative? Can a vector quantity be negative?

thanks

2007-02-25 11:26:40 · 2 answers · asked by wazlakzz 1

Plane

&

Bullet

2007-02-25 11:21:42 · 4 answers · asked by Anonymous

What colour light emerges when a red filter and then a yellow filter is placed in the path of white light?
2) What colour light emerges when a red filter and then a yellow filter is placed in the path of red light?
3) How could you use pigments and/or filtered lighting to make a white object appear violet?
4) How could you use pigments and/or filtered lighting to make a yellow object appear green?

2007-02-25 11:16:31 · 4 answers · asked by Anonymous

A banked circular highway curve is designed for traffic moving at 60 km/h. The radius of the curve is 230 m. Traffic is moving along the highway at 35 km/h on a rainy day. What is the minimum coefficient of friction between tires and road that will allow cars to negotiate the turn without sliding off the road?

2007-02-25 11:11:41 · 2 answers · asked by Anonymous

does the photoelectric effect prove that light is made of particles? do inference experiments prove that light is composed of waves?(is there a distinction between what something is and how it behaves)

2007-02-25 11:00:13 · 1 answers · asked by Bayslappers 1

Why is lettering on the front of some vehicles "backward"

2007-02-25 10:57:37 · 10 answers · asked by Anonymous

A billiard ball of mass mA=0.400kg moving with speed vA=180m/s strikes a second ball, initially at rest, of mss mB=0.400kg. As a result of the collision, the first ball is deflected off at an angle of 30.0° with a speed v'A=1.10m/s.

(a) Taking the x axis to be the original direction of motion of ball A, write down the equations expressing the conservation of momentum for the components in the x and y directions separately.

(b) Solve these equations for the speed v'B, and angle θ, of ball B. Do not assume the collision is elastic.

2007-02-25 10:52:17 · 1 answers · asked by Anonymous

2007-02-25 10:50:26 · 8 answers · asked by morris c 1

I am not sure if i did these right so I'd like someone to double check them before I hand them in...thanks SOO much!

1. A person standing on a bridge at a height of 115m above a river drops a .25kg rock.
-What is the rocks mechanical energy at the time of release..relative to the rivers surface? (I got 282 J)
-What is the rocks kinetic energy after it has fallen 75 m? (98.3 J)...What is the rocks potential energy after 75 m (184J)
6. A .300 kg ball is thrown vertically upward with an inital speed of 10 m/s. If the inital potential energy is called zero, find the balls kinetic, ponetial and mechanical energies at its inital position.
For kinetic i got 15J, for potential its zero and mechanical i got 15 J.
-Now for the balls kinetic, potential and mechanical energies at its maximum height
FOr knetic i said 0 J, for potential i said 15 J and for mechanical i said 15 J.
-Now find the maximum height reached by ball-
I said 5.1 meters

2007-02-25 10:46:31 · 2 answers · asked by Jane A 3

a)What is the volume flow rate: give your answer in litre/minute?

b)What is the Reynolds number for the flow? Comment on the value obtained. (The viscosity of blood is 3.7 mPa s at 37°C, and blood density is 1060 kg/m3.)

2007-02-25 10:44:50 · 2 answers · asked by Lilly G 1

The nearest star beyond the sun is Alpha Centauri which is 4.2 x 10^16 meters away. If we were to recieve a radio message from this star today how long ago would it have been send?

2007-02-25 10:42:03 · 3 answers · asked by Anonymous

On a keyboard you strike middle C, whose frequency is 256Hz

a) What is the period of one vibration of this tone
b) As the sound leaves the instrument at a speed of 340M/s what is its wave lengths in air?

2007-02-25 10:39:37 · 1 answers · asked by Anonymous

A light string 4.00 m long is wrapped around a solid cylindrical spool with a radius of 0.075 m and a mass of 0.500 kg. A 5.00 kg mass is then attached to the free end of the string causing the string to unwind from the spool.
A.) what is the angular acceleration of the spool
B.) How fast will the spool be rotating after all of the string has unwound?

2007-02-25 10:37:13 · 2 answers · asked by Hannah 1

Say we have He in a cylinder with an initial volume of 1 liter and an intial pressure of 1 atm. Somehow, the He expands to a final volume of 3 liters with the pressure rising in direct proportionto its volume. How would you calculate the work done during this process? How could you cause the pressure to rise as the gas expands?

2007-02-25 10:36:27 · 1 answers · asked by chica1012 2

In attempting to pass the puck to a teammate, a hockey player gives it an initial speed of 2.9 m/s. However, this speed is inadequate to compensate for the kinetic friction between the puck and the ice. As a result, the puck travels only one-half the distance between the players before sliding to a halt. What minimum initial speed should the puck have been given so that it reached the teammate, assuming that the same force of kinetic friction acted on the puck everywhere between the two players?

2007-02-25 10:32:09 · 1 answers · asked by dawgs1918 1

How about in the headlights of an automobile?

2007-02-25 10:32:08 · 3 answers · asked by Anonymous

What is the name for the process of a gas going DIRECTLY into a solid. I need to know for science class and i can't find it anywhere! thanks!

2007-02-25 10:21:32 · 3 answers · asked by Anonymous

Can anyone explain what a conservation law is?

2007-02-25 10:19:35 · 2 answers · asked by angelgirl 2

On a keyboard you strike middle C, whose frequency is 256Hz

a) What is the period of one vibration of this tone
b) As the sound leaves the instrument at a speed of 340M/s what is its wave lengths in air?

2007-02-25 10:17:05 · 1 answers · asked by Bayslappers 1

A 2 kg ball of putty moving to the right at 3m/s has a head-on inelastic collision with a 1 kg ball of putty moving to the left at 3m/s. What is the final magnitude and direction of the velocity of the stuck together balls after the collision?

How do I solve this?

2007-02-25 10:06:25 · 3 answers · asked by angelgirl 2

a small 50kg box over a wood floor as compared to pushing a large 50kg box of the same material over the same floor

2007-02-25 09:56:19 · 5 answers · asked by HowDoUGetOut 1

ok this is the problem i was given however i am going to change the #'s.... please help me see how a problem liek this would be set up and how to go through it so i can understand in order to do it for my actual problem ... thank you sooo much....


a boy ( mass 60 kg) falls from rest and hits the ground. during collision he comes to rest in .0100s the avg. force on him by ground is +15000N. (up is postive) form what height did he fall?

it also says to assume only force is collision due to ground....


please help me set this up and see how to interpret a problem set up in this way thank you so much

2007-02-25 09:53:04 · 3 answers · asked by Anonymous

a projectile w/ mass .850 kg is shot up w/ speed of 20 m/s how high would it go if there was no air friction?

I was looking through my book for a possible explanation on this but none of the formulas could i find to do with height? it is hidden w/in a formula and didn't notice... please explain to me how to wrok this out... again id ont expect anyone to do it for me and just give me answer i really do want to learn this stuff but for some reason physics is hard for me... please help me set this up and understand why and how.....

also there is a second part to this problem where they give you a mx height and it says to determine magnitude of average force due to air resistance.... ill workt his out on my own but is there a formula you use for avg force due to air resistance... my book is absolutely no help when it comes to these homework problems thank you

2007-02-25 09:48:01 · 3 answers · asked by Anonymous

conservation of momentum to me. can you give an example where momentum is conserved and one where it isn't.

2007-02-25 09:45:59 · 4 answers · asked by jls10 3

john (mass 80 kg) is skating when he sees his best friend (mass 20 kg) whith his back turned up ahead. He comes behind his friend grabs him and rolls off at 3.0 m/s. What is johns speed before he grabbed friend (ignore friction)



I dontreally know where to begin... i tried a couple of formulas in the book..... can someone talk me through setting up this problem...... also is this elastic or inelastic? i thought it was inelastic so i was using formulas they gave for that so maybe that s what i got wrong or maybe i wasn't plugging things in right.... please talk me through and explain so i can understand this better for my other collision problems thank you

2007-02-25 09:35:58 · 2 answers · asked by vetanimallover 1

hello, i am having problems with one of my hw problems... i am going to change the numbers from the original so i have to work it out myself so if w/ the new numbers someone could explain and talk me through how to do it... such as if there is a formula to use or how to do it i would appreciate it... I'm not sure what i'm not grasping about this it seems like to others its a simple concept so there is something not clicking any help would be appreciated thank you.....

bicyclists with mass 70 kg generates average power of 5.50 W per kilogram of body mass..... how much work is done during 80 km race w/ avg speed 12.0 m/s


please explain thank you

2007-02-25 09:31:03 · 3 answers · asked by Anonymous

1. Three boys are trying to balance on a seesaw which consists of a fulcrum rock acting as a pivot at the center and a light board 3.6m long. Two boys are already on either end. One has a mass of 50kg, and the other a mass of 35kg. Where should the third boy, whose mass is 25 kg, place himself so as to balance the seesaw?

2. Find the tension in two wires supporting a 39kg traffic light with angles 51 and 39 degrees (measured from the ceiling to the wire).

3. A meter stick with a mass of 235 g is supported horizontally by two vertical strings one at the 0cm mark and the other at the 90cm mark. What is the tension in both strings?

4. Three forces are applied to a tree sapling to stabilize it. The the angle between F1 and F2 is 110 degrees. If F1=282N and F2=355N, find F3 in magnitude and degrees. In other words, find the degrees between F1 and F3 for the degrees part of the answer.

2007-02-25 09:30:32 · 1 answers · asked by Patty M 1

what is the equation that relates to wavelength?

2007-02-25 09:14:17 · 7 answers · asked by Ha!! 2