Physics - August 2007

An object is propelled vertically upward with an initial velocity of 20 meters per second. The distance s (in meters) of the object from the ground after t seconds is s = -4.9t^2 + 20t.

(1) When will the object reach a height of 100 meters?

(2) What is the maximum height of the object?

2007-08-24 01:19:19 · 4 answers · asked by journey 1

An object is propelled vertically upward with an initial velocity of 20 meters per second. The distance s (in meters) of the object from the ground after t seconds is s = -4.9t^2 + 20t.

(1) When will the object be 15 meters above the ground?

(2) When will the object strike the ground?

2007-08-24 01:17:59 · 2 answers · asked by journey 1

imagine theres a horizontal planeA bove which the effects of gravity are not felt. any object above the plane just floats and gravity has no influence on it.
now take a chain(for e.g:made of small steel ring) of length hundred metres above the planeA and arrange it so that its in a heap just above the planeA. but take care the chain is not entangled and should be easy to stretch along its length.

now pull the lower end of the thread below the planeA and the chain runs down like a single thread and hits the ground and as links pull down on the ones they are linked to , the whole length of the chain will run like a thread and hit the ground in some time. now take planeA is 20metres above the ground surface. the terminal velocity of links when they hit ground will be around 14 metres .
now consider hundred metres of the chain weighs 100 units. the potential energy of the chain just above the planeA will be m*g*h =100 *9.8*20
=19600 units.

2007-08-24 00:27:06 · 5 answers · asked by balaji.k 2

Assuming we can pass through lavas, etc inside the earths core with some special equipment.

2007-08-23 23:39:26 · 13 answers · asked by Raja S 2

If a plane is travelling faster than the speed of sound but emits no sound. do you still get the sonic boom

2007-08-23 23:34:40 · 8 answers · asked by leerobo 2

1. The sum of two sinusoidal traveling waves is also a sinusoidal traveling wave only if:
A. Their amplitudes are the same and they travel in the same direction.
B. Their amplitude are the same and they travel in opposite direction.
C. Their frequency are the same and they travel in the same direction.
D. Their frequency are the same and they travel in opposite direction.
The answer is C. Why? Does it mean that is their frequency aren’t the same, no traveling wave will be formed?

2. When 450 nm light is incident normally on a certain double slit system, the number of interference maxima within the central diffraction maximum is 5. When 900 nm light is incident on the same slit system the number is:
A. 2
B. 3
C. 5
D. 9
Please show solution and explanation, thanks!

2007-08-23 23:07:35 · 2 answers · asked by MatT 7

1. In displacement vs. time graph, does it represent the period or the wavelength? If so, what represents the other?

2. The displacement of a string carrying travelling sinusoidal wave is given by y(x,t) = A sin (kx-wt+φ). At time t=0 the point at x=0 has a displacement of 0 and is moving in the +y direction. The phase constant φ may take the value of 180 deg. Why?

3. A source of frequency f sends waves of wavelength λ travelling with speed v in some medium. If the frequency is chaged from f to 2f, then the new wavelength and new speed will be? What is the formula/equation to use?
a. λ/2, v or b. λ, 2v

2007-08-23 22:58:00 · 2 answers · asked by MatT 7

The ion particle are accelerated out the back of the space ship using a electrostatic grid. The ion particles are accelerated to a top speed of 100 000 km/h. If you are placing more electrostatic grids along the back of the engine, will the ion particles go faster then 100 000 km/h ?

2007-08-23 21:36:58 · 2 answers · asked by seeker 2

imagine theres a horizontal planeA bove which the effects of gravity are not felt. any object above the plane just floats and gravity has no influence on it.
now take a chain(for e.g:made of small steel ring) of length hundred metres above the planeA and arrange it so that its in a heap just above the planeA. but take care the chain is not entangled and should be easy to stretch along its length.

now pull the lower end of the thread below the planeA and the chain runs down like a single thread and hits the ground and as links pull down on the ones they are linked to , the whole length of the chain will run like a thread and hit the ground in some time. now take planeA is 20metres above the ground surface. the terminal velocity of links when they hit ground will be around 14 metres .
now consider hundred metres of the chain weighs 100 units. the potential energy of the chain just above the planeA will be m*g*h =100 *9.8*20
=19600 units.

2007-08-23 21:29:25 · 2 answers · asked by balaji.k 2

imagine theres a horizontal planeA bove which the effects of gravity are not felt. any object above the plane just floats and gravity has no influence on it.
now take a chain(for e.g:made of small steel ring) of length hundred metres above the planeA and arrange it so that its in a heap just above the planeA. but take care the chain is not entangled and should be easy to stretch along its length.

now pull the lower end of the thread below the planeA and the chain runs down like a single thread and hits the ground and as links pull down on the ones they are linked to , the whole length of the chain will run like a thread and hit the ground in some time. now take planeA is 20metres above the ground surface. the terminal velocity of links when they hit ground will be around 14 metres .
now consider hundred metres of the chain weighs 100 units. the potential energy of the chain just above the planeA will be m*g*h =100 *9.8*20
=19600 units.

2007-08-23 20:47:11 · 2 answers · asked by balaji.k 2

Help me with this...?
a ballA of mass 1 units travelling at velocity of 2 units collides with a ballB of mass 1.2 units which is at rest. take the collision as head on and perfectly elastic. now can u please find the velocities of the balls after the collision using law of cons of momentum...?

2007-08-23 19:29:51 · 2 answers · asked by mikel 2

2007-08-23 18:45:11 · 9 answers · asked by Anonymous

2007-08-23 18:30:15 · 6 answers · asked by Luda R 1

Please help!

A speedboat begins at the rest and accelerates at +2.01 m/s2 for 6.55 s. At the end of this time, the boat continues for an additional 5.80 s with an acceleration of +0.518 m/s2. Following this, the boat accelerates at -1.49 m/s2 for 8.80 s.

(a) What is the velocity of the boat at t = 21.15 s?

(b) Find the total displacement of the boat.

Thank you so much!!!!!!!!!!!!!!!!!!

i posted this earlier but all the answers i got were wrong. i checked them and the computer tells if your right or wrong but not how to do them or what the right answer is so...
please, PLEASE, help me. i desperately need it.

i sincerly appreciate it!

2007-08-23 17:43:03 · 3 answers · asked by Elizabeth 3

2007-08-23 17:11:27 · 4 answers · asked by Anonymous

What are the frequency and wavelength of the light in the glass?

2007-08-23 17:09:16 · 2 answers · asked by Anonymous

If a live wire fell into the middle of a lake, how close could you swim to it before feeling the current? Before being electricuted? Is there a fomula for resistance in fresh water?

2007-08-23 17:01:34 · 4 answers · asked by superbird 4

Yes, we see colour because of surfaces absorbing and reflecting certain wavelengths of light.
What determines the specific colour a particular material, molecule, what have you, would reflect?

p.s. If you know, does it have anything to do with the Hamiltonian eigenvalue problem?

2007-08-23 16:31:45 · 10 answers · asked by Harvey H 1

A speedboat begins at the rest and accelerates at +2.01 m/s2 for 6.55 s. At the end of this time, the boat continues for an additional 5.80 s with an acceleration of +0.518 m/s2. Following this, the boat accelerates at -1.49 m/s2 for 8.80 s.
(a) What is the velocity of the boat at t = 21.15 s?

(b) Find the total displacement of the boat.

Thank you so much!!!!!!!!!!!!!!!!!!

as long as you kinda show some work, you don't need to explain.

2007-08-23 16:23:09 · 2 answers · asked by Elizabeth 3

A long thin rod of length 2L rotates with a constant angular acceleration of 10 rad/s2 about an axis that is perpendicular to the rod and passes through its center.

What is the ratio of the angular speed (at any instant) of a point on the end of the rod to that of a point a distance L/2 from the end of the rod?
a) 1:1
b) 1:2
c) 4:1
d) 1:4
e) 2:1

2007-08-23 16:03:53 · 1 answers · asked by Anonymous

Well?

2007-08-23 12:56:11 · 11 answers · asked by Anonymous

If one twin is in a spacestation and the other is in a ship moving past the station at a high speed, the twin in the ship will have aged less than the one in the station when he returns. (Assume the ship does not stop on return) This is usually explained by the fact that the ship is not an inertial frame because it must accelerate to turn around for the return part of its trip.

But what if the universe is closed and the ship just continues to travel at a constant speed in a straight line until it has gone all the way around the universe and has returned to its starting point? The austronaut never feels any acceleration; this would be an inertial frame. So there is no way to say which twin is "really" moving and which is at rest. The situation is symmetrical for both. So each one should be younger relative to the other.
This seems like a true paradox. Relativity says they can not be the same age. And symmetry says both can claim to have been the one "at rest" and thus the older.

2007-08-23 11:45:03 · 5 answers · asked by Jeffrey K 7

but do any of you also feel that "time" is going much much faster than it ever used to? what do you think this sense of time going so fast is associated with?

2007-08-23 11:17:32 · 8 answers · asked by waterlily750 4

2007-08-23 10:49:54 · 11 answers · asked by nicholas b 2

2007-08-23 09:51:56 · 11 answers · asked by JR e 1

2007-08-23 09:46:32 · 2 answers · asked by Tahpenes S 1

Water has a mass per mole of 18.0g/mol, and each water molecule (H2O) has 10 electrons. a) How many electrons are their in one liter (1.00 x 10 to the negative third mto the third) of water? b) What is the net charge of all these electrons?

2007-08-23 08:42:29 · 3 answers · asked by Diane S 1

2007-08-23 08:33:52 · 3 answers · asked by Alexander 6

So, I'm doing a physics problem, and I ran into a bit of a problem. I am trying to find the force water exerts on a dam - I found that the total force is equal to
(where H = height of water, W = width)

F = (water density)( gravity )( W ) times the

integral from 0 to H of (H - y) dy. where y is the vertical axis

How would I find that integral?

thanks!

2007-08-23 08:11:04 · 2 answers · asked by snoboarder2k6 3

2007-08-23 07:13:28 · 4 answers · asked by soso roro 1