Physics - December 2007

The Big Pot of Soup As part of his summer job at a resturant, Jim learned to cook up a big pot of soup late at night, just before closing time, so that there would be plenty of soup to feed customers the next day. He also found out that, while refrigeration was essential to preserve the soup overnight, the soup was too hot to be put directly into the fridge when it was ready. (The soup had just boiled at 100 degrees C, and the fridge was not powerful enough to accomodate a big pot of soup if it was any warmer than 20 degrees C). Jim discovered that by cooling the pot in a sink full of cold water, (kept running, so that its temperature was roughly constant at 5 degrees C) and stirring occasionally, he could bring the temperature of the soup to 60 degrees C in ten minutes.
How long before closing time should the soup be ready so that Jim could put it in the fridge and leave on time ?

2007-12-16 17:54:35 · 2 answers · asked by Anonymous

heya everyone..
in class 10 syllabus..physics...we got Electricity chapter...

in that one...we have two-three formulas of power..

power = I*I*R
and POWER = V*V / R

so my quesion is...in one case..power is directly proportional to R(resistance) and in second...itz inversely proportional to R...

howz it possible???...plzzz answer asap!!!

2007-12-16 17:20:08 · 3 answers · asked by nikita 2

hey guys, I need help ASAP! this stuff is due 2morrow, please help!


1. 40.2 g sample of metal is heated to 99.3 C and then placed in a calorimeter containing 120. g of water ( s= 4.184 J/gC) at 21.8 C. the final temp of the water is 24.5 C which medal was used?

b. Iron ( s=0.45 J/gC)
c. Copper ( s=.20 J/gC)
d. Lead ( s=.14 J/gC)
e. Silver (.13 j/gC)


2. consider the following:
2A -> 1/2 B + C change in heat = 5 kJ/mol
5/2 B + 4C -> 2A+ C+ 3D change in heat = -15 kJ/mol
E + 4A -> C

Calculate change in heat for: C-> E + 3D
a. 0 kJ/mol
b. 10
c.-10
d.-20
e20 kJ/mol

2007-12-16 17:06:24 · 2 answers · asked by whosethatgurl101 2

1) If the wavelength of light changes as light goes from one medium to another, while the frequency remains the same. If the wavelength is shorter in water than in air, than the following:

a) A certain blue-green light has a wavelength of 600 nm (6x10^-7 m) in air. What is its wavelength in water, where light travels at 75% of its speed in air? __nm

b)What is its wavelength in Plexiglas, where light travels at 67% of its speed in air?__nm

2007-12-16 16:50:52 · 4 answers · asked by TheLostOne 3

scully discovered a ufo. she estimated that the ufo had a mass of 2500 kg traveling at 3600m/min. what is the momentum of the ufo?

a. 11.5 x 10^5 kg m/s
b. 1.5 x 10^4 kg m/s
c. 15,000
d. scully cannot determine the momentum from the information provided

2007-12-16 16:30:18 · 2 answers · asked by Anonymous

A) iron.

B) uranium.

C) lead.

D) hydrogen.

E) plutonium.

2007-12-16 16:25:28 · 8 answers · asked by GC8 1

a golfer can hit a golf ball a horizontal distance of over 300 m on a good drive. what maximum height would a 301.5 m drive reach if it were launched at an angle of 25.0 degrees to the ground?

a. 140.6 m
b. 70.3 m
c. 150.8 m
d. 332 m

huh??!?

2007-12-16 16:15:45 · 3 answers · asked by Anonymous

a 60 kg student on in-line skates is playing with a 25 kg ball. If the student is initially at rest then catches the ball thrown to the right at 4.5 m/s. Explain the change in the student's momentum?

a. no change
b. the student's momentum will be to the right
c. the momentum will be zero
d. the student's momentum will increase while the ball's momentum will decrease

2007-12-16 16:07:37 · 2 answers · asked by Anonymous

Could he return before his twin sister was born? Defend your answer.

2007-12-16 16:06:17 · 3 answers · asked by Anonymous

2007-12-16 16:04:12 · 4 answers · asked by Anonymous

from warmer objects to cooler objects?
from cooler to warmer?
back and forth?
all of the above depending on tempurature?

2007-12-16 15:47:00 · 1 answers · asked by Erica 1

A 55 kg pole-vaulter falls from rest from a height of 5.0 m onto a foam-rubber pad. The pole-vaulter comes to rest 0.30 s after landing on the pad.
a) Calculate that athlete's velocity just before reaching the pad.

b) Calculate the constant force exerted on the pole-vaulter due to the collision.

2007-12-16 15:45:06 · 3 answers · asked by Anonymous

A large mass (500kg) moving 10 m/s to the right collides with a smaller mass (5kg) which is initially at rest. The time of contact during the collision is 5 milliseconds. The large mass continues to travel to the right after the collision but at a reduced speed of 8 m/s.

Questions:

1. What is the magnitude of the force which these objects exert on each other?

2. What is the final velocity of the small mass?

Now reverse the situation. The small mass is moving to the right at 10 m/s and collides into the large mass which is at rest. The speed of the large mass after the collision is 1 m/s to the right (Assume that the time of the contact is the same as the previous example)

Questions:

3. What is the magnitude of the force which these objects exerts on each other?

4. What is the final velocity of the small mass?


Please show me how to solve this problem!

2007-12-16 15:14:14 · 2 answers · asked by Anonymous

air from a balloon, water, book, or a ice cube?


HELP BEST ANSWER!

2007-12-16 15:12:05 · 7 answers · asked by Anonymous

I understand that as we look at stars that we are seeing what happened in the passed due to the time that it took light to reach us. My confusion arises from the fact that at the time of the big bang, all mass was concentrated in a single point. Thus the mass of the star that we are observing and the mass of earth were at the time of the big bang at the same location and then separated at the big bang at a speed less than that of the speed of light. Thus if we look back at an object that is a billion light years away from us, then it must have taken more than a billion years for the particles that originated from the big bang to be separated by a billion light years. (This assumes that the particles raced away from each other at the speed of light). Thus when we see back in time we can never see before the time that it took for the particles to become separated by billion light years. Help!

2007-12-16 15:09:06 · 5 answers · asked by Marv S 1

1.) 0
2.)4
3.)2
4.)+ or - 1/2
5.) 1

2007-12-16 14:41:26 · 5 answers · asked by Anonymous

four climbers have tied themselves together with rope.
They march uphill (20 degrees) with an accel of 1.3 m/s2.
The three climbers behind the leader don't climb at all dragging with a coefficient of .11. the leader does all the climbing.
Find the tension between each rope and the force that that leader applies if their weights are as follows.
Leader 6kg
next 2kg
next 12kg
last 4kg

I dont even know where to start. help me please?

2007-12-16 14:06:05 · 2 answers · asked by Anonymous

Say I want to crete a sort of spiral of space-time or a time funnel/spiral [whatever you want to call it]. Or just warp space so it's bigger in front of you and smaller behind you .This would cause near instantaneous travel over many light years. But it would be difficult getting it to stabalize and have all your atoms put in the right place.

2007-12-16 13:30:52 · 7 answers · asked by Noe V 1

the return trip against the same current took 4 hours. find the speed of the boat in still water

2007-12-16 13:26:43 · 1 answers · asked by Anonymous

it isnt a right triangle.

2007-12-16 13:21:28 · 4 answers · asked by deadly scythe 1

I live near a nuclear reactor which has had its share of unusual events and alerts and I'm wondering if there is a site that logs the emergencies that occur at nuclear reactors in the US.

This information always shows up in the news so I would expect that somewhere out there someone is chronicling it...

Thanks!

2007-12-16 13:20:12 · 1 answers · asked by John 1

how big would the tidal wave be, or how fast, damage

2007-12-16 13:13:34 · 1 answers · asked by Anonymous

Andrea has a mass of 49 kg. She rides the up escalator at Ocean Park in Hong Kong. This is the world's longest escalator, with a length of 227 m and an average inclination of 31°. How much work does the escalator do on Andrea?

I have no idea... any help would be apprecaited

2007-12-16 13:08:21 · 2 answers · asked by Anonymous

2007-12-16 13:04:06 · 4 answers · asked by lizerbeth28 2

An amusement park ride consists of a large vertical cylinder that spins about its axis fast enough that a person inside is stuck to the wall and does not slide down when the floor drops away.
The acceleration due to gravity is 9.8 m/s/s.
Given g = 9.8 m/s/s, the coefficient u=0.444 of static friction between a person and the wall, and the radius of the cylinder R = 3.7 m. For simplicity, neglect the person's depth and assume he or she is just a physical point on the wall. The person's speed is
v= (2 Pi r)/ T
where T is the rotation period of the cylinder
Find the maximum rotation period T of the cylinder which would prevent a 65 kg person from falling down. Answer in units of s.

2007-12-16 12:48:57 · 3 answers · asked by Anonymous

the canon fires at the speed of 30m/s. find the 2 possible angle of the canon that it will hit the top of the tower.

2007-12-16 12:45:54 · 3 answers · asked by samkill 1

2007-12-16 12:45:33 · 1 answers · asked by Anonymous

2007-12-16 12:43:43 · 1 answers · asked by ayessa 1

A child and sled with a combined mass of 48.6 kg slide down a frictionless hill that is 8.02 m high. If the sled starts from rest, what is its speed at the bottom of the hill?

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A person doing a chin-up weighs 755 N, disregarding the weight of the arms. During the first 25.0 cm of the lift, each arm exerts an upward force of 381 N on the torso. If the upward movement starts from rest, what is the person's speed at this point?

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A skier of mass 65.5 kg is pulled up a slope by a motor-driven cable. How much work is required to pull the skier 41 m up a 30° slope (assumed to be frictionless) at a constant speed of 2.0 m/s?

2007-12-16 12:43:41 · 1 answers · asked by Anonymous

for physics

2007-12-16 12:40:53 · 1 answers · asked by ayessa 1