Physics - September 2007

(b)How far would the ball fall in twice that time?

2007-09-11 20:03:28 · 3 answers · asked by Anonymous

Explain why a helicopter with just one main rotor has a second smaller rotor mounted on a horizontal axis at the
rear as in Figure 10-43. Describe the resultant motion of the helicopter is this rear rotor fails during flight.

2007-09-11 19:19:11 · 3 answers · asked by andz 1

Traumatic brain injury such as concussion results when the head undergoes a very large acceleration?
Generally, an acceleration less than 800 m/s2 lasting for any length of time will not cause injury, whereas an acceleration greater than 1000 m/s2 lasting for at least 1 ms will cause injury. Suppose a small child rolls off a bed that is 0.44 m above the floor. If the floor is hardwood, the child's head is brought to rest in approximately 1.9 mm. If the floor is carpeted, this stopping distance is increased to about 1.2 cm. Calculate the magnitude and duration of the deceleration in both cases, to determine the risk of injury. Assume that the child remains horizontal during the fall to the floor. Note that a more complicated fall could result in a head velocity greater or less than the speed you calculate

hardwood floor magnitude______ m/s2 duration ______ ms

Carpeted floor magnitude_______m/s2 duration ______ ms


so far i got...I need to know how to get hardwood and Carpeted floor magnitude


First, calculate the speed of the infant just before impact:

d=.5*g*t^2
t=sqrt(2*.44/9.81)
=.3 sec

speed = g*t
=9.81*.3
=2.94 m/s

Hardwood

Deceleration distance
d=.5*a*t^2
.0019 =.5*a*t^2
a=.0038/t^2
Average speed
v=.5*a*t
=.5*2.94
=1.47
a=2.94/t

Using the equations together
2.94/t=.0038/t^2
t=.0038/2.94
=1.3 ms
a=_____ m/s^2

Hardwood bad

Carpet

The average speed is still the same
a=2.94/t

the deceleration is
a=.0248/t^2

Again solving simultaneously
t=.0248/2.94
=8.4 ms
a=_____ m/s^2

Carpet= no trauma.

Thank you

2007-09-11 17:56:57 · 1 answers · asked by bp 1

2007-09-11 17:12:54 · 1 answers · asked by Peter A Child 1

This is a somewhat advanced question. Suppose that two elastic balls moving through three-dimensional space collide and rebound, conserving both kinetic energy and momentum. The balls cast shadows, and these shadows, moving over a flat two-dimensional surface come together, collide and rebound. Now pretend the shadows have mass. Suppose the the shadow of a ball has a mass porportional to the mass of the ball. Then, the colliding shadows:

a) conserve kinetic energy
b) conserve momentum
c) conserve both kinetic energy and momentum
d) conserve neither kinetic energy nor momentum

2007-09-11 16:56:20 · 1 answers · asked by ? 6

Professor Steven Jones has actually tested steel samples from the towers, he definitely found thermate traces. The one major thing he did point out was 'yellow molten metal' flowing from the impact floors. Its on all the news footage so theres no denying it happened. Now the only material on earth that can flow yellow in a liquid state is thermate (Im no scientist but I would presume its the sulfur that makes it appear yellow.) Now Ive seen the videos, so have millions of people , most without realising what they were looking at. But Steven Jones is a very learned man, he studies things like this, and I believe what he has found is definite proof of thermate cutting charges. If you believe Bush's story or not you need to watch a free to air doco called "911 Mysteries" it offers up a multitude of reasons why 911 happened the way it did, most if not all of them scarily believable.....
The film maker Sofia Smallstorm cannot tell you that it definitely was an inside job, all she does is present the facts and once youve watched it you will start thinking....that much I can promise you.
And one more thing while Im here........the Bush apologists will always argue that the steel didnt need to melt to cause the floors to collapse, thats fair enough BUT. What they expect us to believe is that the support clips all failed at the impact floors which caused a pancake effect right??? Seems like a reasonable argument, even the official report tells us the floors pancaked. But there is one major flaw that they cant explain and Ill tell you what it is. For a floor to pancake it has to fall through space to hit the floor beneath it, this breaks the supports holding up the lower floor and so on (about 80 times till the mass reaches ground level.) now even if we give each floor an amazingly fast half second to travel through that space crushing all the support steel, girders, steel mesh, interior walls, office furniture etc, the real world time for the impact floors to reach ground level should have been around 40 seconds!!! (thats 80 storeys collapsing in a half second each!!!!
That plainly did not happen because THERE WAS NO PANCAKING!!!! The towers dropped within 14 seconds, almost as fast as freefal speed!!! And the only way that could have happened was by severing the 48 steel columns at the core, and probably severing the foundation steel in the basements also, there is no two ways about it.
The Bush apologists physics dont hold up to scrutiny, they dont hold up to critical analysis, and why so many videos all over the net showing survivors and firemen, cops and reporters all mentioning explosions inside the buildings?

2007-09-11 16:46:57 · 10 answers · asked by Anonymous

i think no one will ever built a time machine it is very improbable and for those who '' know every single answer..''
the answer to this question is NEVER !!
give me a feed back you ''geniuses'' out there..

2007-09-11 16:41:05 · 5 answers · asked by roman d 1

2007-09-11 16:38:41 · 1 answers · asked by Jonathan B 1

1) For the ballistic missile aimed to achieve the maximum range of 1000 km, what is the maximum altitude reached in the trajectory in km.

2) For the intercontinental ballistic missile to have a range of 10,500 km, what must be the speed (v0) of the missile at the end of the acceleration phase? Take the distance of the acceleration phase, as negligible compared to the travel time. Answer in km/s.

2007-09-11 16:38:04 · 2 answers · asked by lola 1

Stephanie serves a volleyball from a height of 0.79 meters and gives it an initial velocity of +6.7 meters per second straight up. How high will the volleyball go??

2007-09-11 16:09:21 · 1 answers · asked by lexxon0121 1

Two cars are traveling along a straight-line in the same direction, the lead car at 25.0 m/s and the other car at 33.0 m/s. At the moment the cars are 40.0 m apart, the lead driver applies the brakes, causing his car to have an acceleration of -1.90 m/s2.

(a) How much time does it take for the lead car to stop?
-----------s
(b) Assuming that the chasing car brakes at the same time as the lead car, what must be the chasing car's minimum negative acceleration so as not to hit the lead car?
--------m/s2
(c) How much time does it take for the chasing car to stop?
----------s

I am completely lost here, can someone please explain or at least help me in getting started off? Thanks so much!

2007-09-11 15:47:21 · 2 answers · asked by me 1

A person walks 47 m East and then walks
31 m at an angle 44 degree North of East.
What is the magnitude of the total dis-
placement? Answer in units of m^2?

2007-09-11 15:47:05 · 1 answers · asked by Cantthinkofanickname 1

A projectile is shot from the edge of a cliff h = 305 m above ground level with an initial speed of v0 = 105 m/s at an angle of 37.0° with the horizontal.

(a) Determine the time taken by the projectile to hit point P at ground level= .... s

(b) Determine the range X of the projectile as measured from the base of the cliff = .... m

(c) At the instant just before the projectile hits point P, find the horizontal and the vertical components of its velocity. (Take up and to the right as positive directions.)
horizontal= ... m/s
Vertical= .... m/s

(d) What is the the magnitude of the velocity?.... m/s

(e) What is the angle made by the velocity vector with the horizontal?

(f) Find the maximum height above the cliff top reached by the projectile.
...... m

2007-09-11 15:46:56 · 2 answers · asked by Nikita 1

(a) What was the takeoff speed? .... m/s
(b) If this speed were increased by just 6.0%, how much longer would the jump be? .... m

and also, this question : 2). A hunter aims directly at a target (on the same level) 120 m away.

(a) If the bullet leaves the gun at a speed of 200 m/s, by how much will it miss the target?
(b) At what angle should the gun be aimed so as to hit the target?



Please help me to do this problem and also please include the work. Thank you soo much for helping me to do this.. Thank You :)

2007-09-11 15:29:36 · 2 answers · asked by Nikita 1

help! :)

2007-09-11 15:07:34 · 4 answers · asked by itskelc 1

A block on a loop-the-loop slides without friction. The radius (R) of the loop is 2.5m and the point (B) is the highest position of the loop. If the block starts from a sufficent height (h), it will exert a force (F) to the track when it comes to (B). Find the height (h) when the force (F) is equal to the block's weight.

2007-09-11 14:47:00 · 1 answers · asked by Anonymous

I am doing a physics problem and i have a volume of 1000 cm^3 and a diameter in meters.

i need to convert them into the same units so i can solve the problem

2007-09-11 14:39:28 · 6 answers · asked by Nick S 2

In 1865, Jules Verne proposed sending men to the Moon by firing a space capsule from a 220 m long cannon with final speed of 10.97 km/s. What would have been the unrealistically large acceleration experienced by the space travelers during their launch? (A human can stand an acceleration of 15g for a short time.)

---------- m/s2

I am unsure how to solve this problem. I know that acceleration is change in velocity over change in time. I started out by converting the km per sec to meter per second and got 10970 m/s but dont know where to go from here. Am I starting the right way? Can someone please help? Thanks!

2007-09-11 14:32:27 · 3 answers · asked by me 1

How far from the base of the cliff does ali land?

Two part answer.

2007-09-11 14:29:58 · 1 answers · asked by Tenzin 1

An object fall from height h from rest and travels 0.5h in the last 1.00s. Find the time of its fall.

Thanks!

2007-09-11 14:23:01 · 6 answers · asked by Anonymous

Two SPHERICAL objects have the same mass. One floats on water; and the other sinks. Which Object has greater diameter?

2007-09-11 14:20:58 · 6 answers · asked by Nhat t 1

Suppose a treadmill has an average acceleration of 4.7 * 10^ -3 m/s^2

a) How much does its speed change after 5.0 min?
To find this I used the formula a=v/t (Acceleration = velocity / time) and when I solved it I got 1.41 m/s.

b) If the treadmill initial speed is 1.7 m/s, what will its final speed be?

In this second question I don't even know where to start. Can someone help me please?
Thank You! :D

2007-09-11 14:17:42 · 6 answers · asked by . 6

2007-09-11 14:07:40 · 3 answers · asked by rmsboy51 1

is it possible to create a thermobaric explosion that would consume all the oxygen in the atmosphere?

If so what would be the effects (does it produce CO2 or CO)?

2007-09-11 14:03:40 · 3 answers · asked by delprofundo 3

Always been curious. I don't doubt the big bang, but where did all that matter come from before it got dense, and then exploded? Or is this one of the things that we still don't have a clue about?

2007-09-11 13:58:14 · 9 answers · asked by Jesse G 1

Besides the Medium

2007-09-11 13:34:55 · 1 answers · asked by Tony 2

A car starts from rest and travels for 4.9 s with a uniform acceleration of +1.2 m/s2. The driver then applies the brakes, causing a uniform acceleration of -2.2 m/s2. The breaks are applied for 1.70 s.

(b) How far has the car gone from its start?

2007-09-11 13:33:43 · 2 answers · asked by Anonymous

A parachutist descending at a speed of 9.40 m/s loses a shoe at an altitude of 31.60 m.

(b) What is the velocity of the shoe just before it hits the ground?

2007-09-11 13:32:14 · 2 answers · asked by Anonymous

A boy sledding down a hill accelerates at 1.20 m/s2. If he started from rest, in what distance would he reach a speed of 5.00 m/s?
dont need work just need answer

2007-09-11 13:32:05 · 1 answers · asked by Anonymous

A clothesline has a mass M, and each end makes an angle X with the horizontal. What is a) the tension at the ends of the clothesline? b) the tension at the lowest point? The curve is hanging under it's own weight (catenary curve).

2007-09-11 13:11:35 · 3 answers · asked by J 1