Physics - October 2007

2007-10-07 21:05:41 · 4 answers · asked by yien 1

A 50 grams of metal at 95 degree celcius is dropped into 250 grams of water at 17 degree celcius and warms it up to 19.4 degree celcius. What is the specific heat(c) of the metal?

2007-10-07 21:00:36 · 3 answers · asked by yien 1

A device operates at 6 volts and has a power rating of 4 watts. It is connected to a 240 volts a.c supply, using a suitable transformer.

-If the primary coil of the transformer has 4000 turns, how many turns are on the secondary coil?

-Calculate the current flowing in the primary coil?

Please explain, thanks!

2007-10-07 20:27:25 · 3 answers · asked by misseighteen 3

A frictionless roller coaster is given an intial velocity of Vo at height h=30m. The radius of curvature of the track at point A is R=28m. The acceleration of gravity is 9.8m/s2.

Find the maximum value of Vo so that the roller coaster stays on the track at A solely because of gravity.

2007-10-07 20:15:15 · 1 answers · asked by michael 1

2007-10-07 19:21:22 · 4 answers · asked by Unni h 1

2007-10-07 17:39:39 · 3 answers · asked by nancy c 1

Just a silly question but it interests me.

If I was to lay under an X - Ray machine set up for a chest X - Ray, and it was turned on and left on continuiously so I had X- Rays pumping through me all the time, how long would it be until I began to feel something - would it get warm?? How long would it take me to die and get a lethal dose?

2007-10-07 17:16:40 · 5 answers · asked by lucylonglegs 1

2007-10-07 16:42:57 · 6 answers · asked by aienboy 1

A rock is thrown vertically upward with a speed of 12.0 from the roof of a building that is 70.0 above the ground. Assume free fall.
Part A
In how many seconds after being thrown does the rock strike the ground?



Part B
What is the speed of the rock just before it strikes the ground?

2007-10-07 15:59:15 · 1 answers · asked by Mallory 1

Suppose you had a car that was mostly wheels and another car that had tiny wheels. if the cars have the same total mass and their center-of-masses are equal distances from the ground and each goes from zero to 40 mph in ten seconds, which one will nose up the most?

a) Muscle Head
b) Pip Squeak
c) Both the same

2007-10-07 15:31:20 · 2 answers · asked by ? 6

A 120.0 volt motor draws a current of 7.80 A when running at normal speed. The resistance of the armature wire is 0.670 ohms.

(a) Determine the back emf generated by the motor.

(b) What is the current at the instant when the motor is just turned on and has not begun to rotate?

(c) What series resistance must be added to limit the starting current to 15.0 A?

2007-10-07 15:21:50 · 1 answers · asked by Anonymous

A ball swings in a vertical circle at the end of a 1.30 m long rope. When the ball is 37.5° past the lowest point on its way up, its total acceleration is (-22.5 i + 20.2 j) m/s2.

Determine the magnitude of its radial acceleration.
(in m/s2)

Determine the speed and velocity of the ball.


I 'm not sure how to solve this problem... I know the basic rotational motion equations, but this is too complicated for me. What I really need is a vector diagram showing the components of its acceleration at that instant, so if anyone could do that for me (in paint or something), that'd be great. Or just show me how to solve the problem.
Thanks.

2007-10-07 15:09:52 · 2 answers · asked by The Rationalist 2

I would love it if you could explain it in terms of a free falling objects.

2007-10-07 15:02:10 · 1 answers · asked by Mallory 1

The determined coyote is out once more in pursuit of the elusive roadrunner. The coyote wears a pair of Acme jet-powered roller skates, which provide a constant horizontal acceleration of 13.0 m/s2 (Fig. P4.65). The coyote starts at rest 70.0 m from the brink of a cliff at the instant the roadrunner zips past him in the direction of the cliff.

Figure P4.65

(a) The roadrunner moves with constant speed. Determine the minimum speed he must have so as to reach the cliff before the coyote.
m/s
(b) At the edge of the cliff, the roadrunner escapes by making a sudden turn, while the coyote continues straight ahead. The coyote's skates remain horizontal and continue to operate while he is in flight so that his acceleration while in the air is (13.0 - 9.80) m/s2. The cliff is 100 m above the flat floor of a wide canyon. Determine where the coyote lands in the canyon.

Your answer differs from the correct answer by 10% to 100%. m (from base of cliff)
(c) Determine the components of the coyote's impact velocity. (Assume right is the positive x direction and up is the positive y direction.) vx = m/s
vy = m/s

2007-10-07 14:42:59 · 1 answers · asked by Anonymous

A person standing at the top of a hemispherical rock of radius R = 13.00 m kicks a ball (initially at rest on the top of the rock) to give it horizontal velocity vi as in Figure P4.62.

Figure P4.62

(a) What must be its minimum initial speed if the ball is never to hit the rock after it is kicked?
m/s
(b) With this initial speed, how far from the base of the rock does the ball hit the ground?

2007-10-07 14:42:07 · 1 answers · asked by Anonymous

A 120 kg refrigerator is 80 cm square (whats that mean) and 2 meters tall. the coefficient of friction between the fridge and the floor is .25. How much force will it take to push it across the floor upright position? How much force if it's laid on one side? All I know is I have to use the Ff formula but what baffles me is how to get a Newton into the formula. Plz help, I know I have to know this for a test.

2007-10-07 14:34:29 · 5 answers · asked by Anonymous

What are the components and length of a vector which is the sum of the two vectors, V1 and V2, whose components are (2.2, 2.0, 0.0) and (4.9, -4.1, -0.4)

components (____),(____),(_____).

Length (____)

I can get the components but the lenght will not come out for me

2007-10-07 13:55:52 · 1 answers · asked by Albert treeter 2

ty to who helped me with 1 and 2! I was able to get to 9 (this number), hopefully i can get to 16 after this.

please help me understand what to do. i see my knowns are m=45 kg, speed=50m/s. I dont know what the period of acceleration is used for though...

A golf ball with a mass of 45 g is struck by a club, leaving the tee with a speed of 1.8 * 10² km/h. The period of acceleration was 0.50 m/s.

a) What is the average acceleration on the ball as it was struck (in m/s²)?

b)What is the froce exerted on the club?

c)What is the force exerted on the club by the ball?

2007-10-07 13:49:29 · 3 answers · asked by iSmile 2

in which car would you be moving fastest in at the very bottom of a rollercoaster's incline?

a. front car
b. middle car
c. rear car
d. other

2007-10-07 13:40:53 · 1 answers · asked by Nikki 1

A model rocket is launched straight upward with an initial speed of 46.1 m/s. It accelerates with a constant upward acceleration of 1.85 m/s2 until its engines stop at an altitude of 153 m. What is the maximum height reached by the rocket?

Like how do you do this? You don't have to give me the answer, but the process.

thank you so much.

2007-10-07 13:38:29 · 1 answers · asked by lifeisgood20 2

2007-10-07 13:38:17 · 1 answers · asked by Anonymous

2007-10-07 13:23:24 · 1 answers · asked by Anonymous

2007-10-07 13:20:15 · 1 answers · asked by Anonymous

2007-10-07 12:49:21 · 3 answers · asked by Anonymous

I have some homework to do, and it says,

Use a diagram to illustrate each term for a wave.
a. wavelength
b. amplitude
c. cycle - I HAVE NO IDEA WHAT THIS IS.

can somebody explain it to me? i know what wavelength and amplitude is.

THANKS!!!!!

2007-10-07 12:39:32 · 2 answers · asked by Angel D 1

A sled of mass 50kg is pulled along snow-covered, flat ground the static friction coefficent is 0.30, and the sliding friction coeffiecent is 0.10

2007-10-07 12:27:15 · 1 answers · asked by derfla J 1

A force f vector = (4x i + 4y j ) N acts on an object as it moves in the x direction from the origin to x = 5.06 m. Find the work W = integral( f vector·dr ) done by the force on the object.

2007-10-07 11:53:04 · 1 answers · asked by rock it ! 1

and you exert a force F on the free end of the cord.
(a) What must be the magnitude of F if you are to lift the canister at a constant speed?
N
(b) To lift the canister by 2.6 cm, how far must you pull the free end of the cord?
cm
(c) During that lift, what is the work done on the canister by your force (via the cord)?
J
(d) What is the work done on the canister by the gravitational force on the canister?
J

2007-10-07 11:29:23 · 1 answers · asked by Wonder 2

55kg person rides a bike with all her weight on each pedal while climbing a hill.the pedals have a 17 cm radius, what is the max torque? how could she exert more?

2007-10-07 11:22:24 · 2 answers · asked by Richard Gozinya 2

A small mass m is set on the surface of a sphere. If the coefficient of static friction is µs = 0.86, at what angle would the mass start sliding?
I have no idea how to approach this...please help
and thank you in advance

2007-10-07 11:19:43 · 1 answers · asked by hermionegranger 2