Physics - September 2007

The Kentucky Derby is held at the Churchill Downs track in Louisville, Kentucky. The track is one and one-quarter miles in length. One of the most famous horses to win this event was Secretariat. In 1973 he set a Derby record that has never been broken. His average acceleration during the last four quarter-miles of the race was +0.0105 m/s2. His velocity at the start of the final mile (x = +1609 m) was about +16.58 m/s. The acceleration, although small, was very important to his victory. To assess its effect, determine the difference between the time he would have taken to run the final mile at a constant velocity of +16.58 m/s and the time he actually took. Although the track is oval in shape, assume it is straight for the purpose of this problem.

2007-09-12 16:38:57 · 1 answers · asked by lonelygirlinhell 1

2007-09-12 16:26:29 · 3 answers · asked by Geanine J 1

A particle's circular motion in the x-y plane is given by the equations: r(t) = 4.86m, theta(t) = (9.96rad/s)t, where r is the distance from te origin and theta is the polar angle measured counterclockwise from the positive x-axis. What is the x-coordinate of the particle at time t = 3.40s?

2007-09-12 16:18:17 · 2 answers · asked by Anonymous

A ranger in a national park is driving at 54 km/h when a deer jumps onto the road 55 m ahead of the vehicle. After a reaction time of t s, the ranger applies the brakes to produce an acceleration of -3 m/s2. What is the maximum reaction time allowed if the ranger is to avoid hitting the deer?

* i got 40 sec. but the answer was wrong.. i don't get it.

2007-09-12 16:07:33 · 3 answers · asked by wonderer 1

A sports car is advertised to be able to stop in a distance of 50 m form a speed of 90 km/h. What is its acceleration in m/s^2. How many g's is this (g=9.80 m/s^2).

2007-09-12 16:02:53 · 1 answers · asked by nirmal 1

A diver springs upward with an initial speed of 2.44 m/s from a 3.0-m board. (a) Find the velocity with which he strikes the water. [Hint: When the diver reaches the water, his displacement is y = -3.0 m (measured from the board), assuming that the downward direction is chosen as the negative direction.] (b) What is the highest point he reaches above the water?

2007-09-12 15:53:33 · 3 answers · asked by lonelygirlinhell 1

A motorcycleist is going to try to jump across as many buses as he can. The takeoff rampy-thing makes an angle = 18.4 degrees above the horizontal.The landing ramp is identical to the takeoff ramp. The buses are parked side by side, and each bus is 2.74 m wide. The dud leaves the ramp with a speed of v = 31.0 m/s. What is the maximum number of buses over which the guy can jump?

i am so confussed and i have no idea how to do this!!!!!! i just don't even know where to start. please help me. i really am trying and im tired and i need to know how to do this last problem. i have finished the rest of my physics problems and i am just stumped! please help me. Thank you so much!!!!!!!!!!!!

2007-09-12 15:44:44 · 3 answers · asked by Elizabeth 3

Are the electrons in a superconducter "loose" enough to be moved by the radiation from radioactive waste? If a superconducting container were constructed to hold radioactive waste, could it generate electricity?

2007-09-12 15:38:50 · 1 answers · asked by bentoro2001 1

At t = 0, a particle is located at x = 25 m and has a velocity of 15 m/s in the positive x direction.What is the velocity of the particle at t = 5.0 s? [Hint: Find the equation of the line and integrate it]

2007-09-12 15:37:50 · 2 answers · asked by Anonymous

A proton accelerates from rest in a uniform
electric field of 678 N/C. At some time later,
its speed is 2.2 x10^6 m/s.
What is the magnitude of the acceleration
of the proton?

How long does it take the proton to reach this
speed

How far has it moved in this time interval

2007-09-12 15:22:55 · 3 answers · asked by TheThing 2

An electron is released a short distance above
Earth's surface. A second electron directly
below it exerts an electrostatic force on the
first electron just great enough to cancel the
gravitational force on it.

The value of Coulomb's constant is
8.98755x 10^9 N / m2xC2 and the acceleration
of gravity is 9.81 m/s^2 :
How far below the first electron is the second?

2007-09-12 15:20:29 · 2 answers · asked by TheThing 2

Ok, this seems like a simple enough problem, however I have trouble wrapping my mind around physics concepts and trying to set up these problems. Any help will be greatly appreciated. Here is how the problem reads:

Two identical pellet guns are fired simultaneously from the edge of a cliff. These guns impart and initial speed of 30.0 m/s to each pellet. Gun A is fired straight upward, with the pellet going up and then falling back down, eventually hitting the ground beneath the cliff. Gun B is fired straight downward. In the absence of air resistance, how long after pellet B hits the ground does pellet A hit the ground?

As much detail as you can include will help me greatly. I have quite a few of these problems to work and hope I can use this as an example. Thanks again to anyone who tries this.

2007-09-12 15:16:34 · 1 answers · asked by doubtful 2

In coming to a stop, a car leaves skid marks 92 m long on the highway. Assuming a deceleration of 7.00 m/s^2, estimate the speed of the car just before braking.

Walkthrough please; I need to know how to do these not just the answer.

2007-09-12 15:16:20 · 2 answers · asked by ? 2

What do you think about the amateur scientist that found that it was possible to burn salt water. Do you think that there will be some government limitations on salt water? Or that machine will never come to reality because of some kind of restrictions. Is burning saltwater even possible without a additive. Or is this the holy grail in alternative energy?

2007-09-12 15:12:36 · 4 answers · asked by Ollie Williams 2

"Cube A has a volume of 2cm x 2cm x 2cm. What is its density?" How can you find the density of the block with only knowing the volume?

2007-09-12 15:09:15 · 2 answers · asked by Lynn 2

2. An automobile traveling along a straight road increases its speed from 30.0 m/s to 50.0 m/s in a distance of 180 m. If the acceleration is constant, how much time elapses while the auto moves this distance?

2007-09-12 15:02:07 · 4 answers · asked by Anonymous

physics... why can an object accelerate at a constant speed, but not at a constant velocity?

2007-09-12 14:42:25 · 4 answers · asked by theawesomenessofhannah 1

2007-09-12 14:32:33 · 1 answers · asked by Anonymous

A particle moving along the x axis is located at 14.9m at 1.45s and 4.02m at 2.9s. What is the displacement during this time interval? What is the average velocity during this period? What would the average speed be?
Thanks in advance

2007-09-12 13:55:42 · 3 answers · asked by Anonymous

How long could a person spin around in circles in a chair? and if spinning counter clock-wise, how long would it be before they felt the effects of traveling back through time? and how much spinning would it take before the spinner inevitably died?

2007-09-12 13:49:05 · 2 answers · asked by bette2705 1

(a) What is this speed in kilometers per hour?
km/h
(b) What is this speed in meters per second?
m/s

2007-09-12 13:45:07 · 2 answers · asked by Jonathan P 1

2007-09-12 13:33:43 · 3 answers · asked by Anonymous

Since it doesn't have anything in it, why does it absorb heat?

2007-09-12 13:29:32 · 2 answers · asked by Anonymous

Thanks in advance... I tried using the equation y=vt + 1/2at^2 but I think rearranging the equation is not something I'm doing right.

2007-09-12 13:26:32 · 1 answers · asked by bouncing_soul_geuse 2

A football player attempts a 40-yd field goal. If he is able to impart a velocity U of 120 ft/sec to the ball, compute the minimum angle Theta for which the ball will clear the goal, which has a height of 10 feet. Let the mass of the ball be tan(theta). Yes, the mass of the ball depends on the angle.

2007-09-12 13:23:46 · 1 answers · asked by Charlie4590 2

An engineer in a locomotive sees a car stuck on the track at a railroad crossing in front of the train. When the engineer first sees the car, the locomotive is 290m from the crossing and it's speed is 20m/s . If the engineer's reaction time is 0.3s, What should be the magnitude of the minimum deceleration to avoid an accident?

2007-09-12 13:17:48 · 4 answers · asked by Anonymous

2007-09-12 13:08:19 · 2 answers · asked by Carol 1

A motorcycle daredevil is attempting to jump across as many buses as possible. The takeoff ramp makes an angle = 18.6° above the horizontal, and the landing ramp is identical to the takeoff ramp. The buses are parked side by side, and each bus is 2.74 m wide. The cyclist leaves the ramp with a speed of v = 32.0 m/s. What is the maximum number of buses over which the cyclist can jump?

2007-09-12 13:06:19 · 1 answers · asked by Santina E 1

An object held in the air has a GPE of 470J. The object is then dropped. Halfway down, what is the objects kinectic energy?

A system has a total mechanical energy of 350J and a kinetic energy of 220J. what is the potential energy?

2007-09-12 13:05:46 · 1 answers · asked by (>_<) 3

constant speed of the horse is 10.0 m/s, and the man is initially 3.00 m above the level of the saddle. (a) what must be the horizontal distance between the saddle and the limb when the man makes his move? (b) how long is he in the air?

2007-09-12 13:04:54 · 1 answers · asked by mary s 1