Physics - September 2007

Which of the following statements is NOT true of covalent compounds?

a.they form when atoms of two elements share electrons.

b.they have weaker bonds than ions in crystal lettuce

c.they are composed of independence particles called molecules.

d.they have a higher melting point than ionic compounds.

Why dont water and oil mix?


Most soltions that contain molecules of covalent compounds do not conduct an electric current. True or False

Lemon changes the color of tea because the lemon contains a substances called a(n) ________. (acid or base)

2007-09-27 12:53:52 · 2 answers · asked by Anonymous

If you are in a car that is struck from behind, you can receive a serious neck injury called whiplash.

Using Newton's laws of motion, explain what happens.
How does a headrest reduce whiplash?

2007-09-27 12:37:29 · 3 answers · asked by Anonymous

A cannon, located 60.0 m from the base of a vertical 25.0 m tal cliff, shoots a 15 kg shell at 43.0 degrees above the horizontal toward the cliff.

a) What must the minimum muzzle velocity be for the shell to clear the top of the cliff?

b) The ground at the top of the cliff is level, with a constant elevation of 25.0 m above the cannon. Under the conditions of part (a), how far does the shell land past the edge of the cliff?

2007-09-27 12:36:55 · 1 answers · asked by Anonymous

a hockey player hits a puck with his stick giving the puck an initial speed of 5 m/s. if the puck slows uninformly and comes to rest in a distance of 20 m what is the coefficient of kinetic friction between ice and the puck??????

2007-09-27 12:35:41 · 1 answers · asked by hahahaha 2

Famer attaches 25kg bale of hay to one end of rope passing over a frictionless pulley connected to beam in hay barn. Another farmer pulls down on opposite end of rope with force of 277 N. Ignoring mass of rope, what will be the magnitude and direction of the bale's acceleration if the gravatational force acting on it is 245 N?

2007-09-27 12:31:07 · 4 answers · asked by Phil 2

I have a row of plastic pinwheels in my garden, six are 6 to 8 inches big and three are 10 to 12 inches big. When the wind blows and all the pinwheels are spinning, why do the small pinwheels spin counterclockwise and the big pinwheels spin clockwise? Does it have anything to do with the size of the pinwheels?

2007-09-27 12:19:01 · 2 answers · asked by smibgal 1

2007-09-27 12:16:14 · 4 answers · asked by la$t drinx$ 3

airplane flies parallel to the ground, undergoes 2 consecutive displacements.
the first is 39 km at 34.9 degrees west of north
the 2nd is 128 km at 61.1 degrees east of north

at what angle east of north is the plane's total displacement? answer in units of degrees

2007-09-27 12:03:04 · 2 answers · asked by lalalallalallalalal l 1

True or false (yes or no, 1 or 0) problems with wrong-answer penalties:
a) 75-ohm cable are used for analog transmission
b) Single-mode fiber are more expensive but are widely used for longer
distances than multi-mode fiber
c) Downlink are always have higher frequency than uplink for satellite
communication
d) We need at least 4 geostationary satellites to cove the whole earth
surface

2007-09-27 12:01:54 · 1 answers · asked by student 1

2007-09-27 11:47:49 · 1 answers · asked by jovy_rjl 1

An electric heater draws a current of 5.9A when it is plugged into a 120 V household power supply. How much does it cost if this heater is operated for 3.5 hours with 120 V household power supply? ( electrical energy costs 13 cents per KWh

Please show work

2007-09-27 11:42:20 · 2 answers · asked by mastersource2005 5

A rocket is launched at an angle of 53.0° above the horizontal with an initial speed of 99 m/s. The rocket moves for 3.00 s along its initial line of motion with an acceleration of 32.0 m/s2. At this time, its engines fail and the rocket proceeds to move as a projectile.
(a) Find the maximum altitude reached by the rocket.
(b) Find its total time of flight
(c) Find its horizontal range

I tried plugging in a few equations but i cant even seem to find A.

2007-09-27 11:18:08 · 1 answers · asked by Paul Z 1

Tow idenical cannons are aimed at each other, ir shells fired simutanously at exactly the same speeds. Ignoring wind resistance for a moment, will hey hi or miss?

2007-09-27 11:08:37 · 6 answers · asked by ppange12 2

is this right?...
mass is equal to the amount of matter in an object.

mass is equal to energy

if you add energy to an object, then are you also adding matter? where does this matter come from and go?

2007-09-27 10:52:34 · 2 answers · asked by brennanjones123 1

if I had a soccer ball a penny a bowling ball a car and a person to throw out a plane what would hit the ground first?

2007-09-27 10:45:26 · 4 answers · asked by stickerbush1970 2

2007-09-27 09:57:12 · 4 answers · asked by Lambi L 1

A ski jumper travels down a slope and leaves the ski track moving in the horizontal direction with a speed of 30 m/s. The landing incline falls off with a slope of 28º.
a. How long is the ski jumper air borne?
b. Where does the ski jumper land on the incline?

2007-09-27 09:48:50 · 1 answers · asked by sciguy 1

A capacitor has a capacitance of 3.1 x 10^-5 F. In the charging process, electrons are removed from one plate and placed on the other plate. When the potential difference between the plates is 580 V, how many electrons have been transferred?

2007-09-27 09:39:25 · 1 answers · asked by Anonymous

An empty parallel plate capacitor is connected between the terminals of a 15.7-V battery and charges up. The capacitor is then disconnected from the battery, and the spacing between the capacitor plates is doubled. As a result of this change, what is the new voltage between the plates of the capacitor?

2007-09-27 09:36:43 · 1 answers · asked by hemang p 1

And if it is a form of perpetual motion, would a device exhibit perpetual motion if it were in space rather than on Earth which has more gravity and air friction?

2007-09-27 09:34:14 · 4 answers · asked by eoc1000 2

Just as a balloon expands and contracts because of the air pressure difference in and outside of it, could the (area, dimension, space) that the universe is expanding in to have a negative or positive (pressure) that controls the universe's expansion instead of gravity????

2007-09-27 09:23:27 · 3 answers · asked by bagua1 5

As a rocket is fired from a launching pad, its speed and acceleration increase with time as its engines continue to operate. Explain why this occurs even though the thrust of the engines remains constant.

2007-09-27 09:06:40 · 3 answers · asked by back2back 2

2007-09-27 08:48:34 · 12 answers · asked by Angelique 2

A 2.00 m tall basketball player is standing on the floor 10.0 m from the basket, as in Figure P3.58. If he shoots the ball at a 40.0° angle with the horizontal, at what initial speed must he throw the basketball so that it goes through the hoop without striking the backboard? The height of the basket is 3.05 m.

2007-09-27 08:41:44 · 2 answers · asked by Anonymous

A large piece of wood, of mass 80 kg, falls over a waterfall and into the drop pool below. It enters the pool travelling at 20 ms-1 and is then subject to an upwards acceleration of 12 ms-2 due to its buoyancy. How long does it take before it bobs to the surface of the pool?

2007-09-27 08:10:59 · 1 answers · asked by robinf1988 1

A cable is lifting a construction worker and a crate, as the drawing shows. The weights of the worker and crate are 971 N and 1450 N, respectively. The acceleration of the cable is 0.620 m/s2, upward. What is the tension in the cable (a) below the worker and (b) above the worker?

2007-09-27 07:29:43 · 2 answers · asked by sweet_dreams 1

Two crates, of mass m1 = 60 kg and m2 = 110 kg, are in contact and at rest on a horizontal surface (Fig. 4-54). A 620 N force is exerted on the 60 kg crate. The coefficient of kinetic friction is 0.15.

a) Calculate the acceleration of the system.
=............ m/s^2 (to the right)

(b) Calculate the force that each crate exerts on the other.
=.......N

(c) Repeat with the crates reversed.
acceleration =......m/s2
crate force=........ N

2007-09-27 06:40:01 · 1 answers · asked by Nikita 1

Or is it just another theory made up by some wacky scientists?

2007-09-27 06:31:02 · 6 answers · asked by Anonymous

Is the contraction of objects traveling at very high speeds real, or is it juast a optical phenomenon, an ilusion? Why does it happen? What do pepole actually know about it until now? was it proved through experiments, like time dilation, or is it just a completely theoretical thing?

It seems pretty normal to me that we percive objects traveling at high speeds longer, but that's just the eye fooling us, and it's got mothing to do with phizics.

2007-09-27 06:26:07 · 4 answers · asked by vlad r 3

Suppose you take a state machine(a machine who's output is dependant on its inputs and the internal state of the machine) and take the dimension of time and turn it into a 4th spacial dimension, would we then have a 4 dimensional combinational machine(a machine whos outputs are only dependant on its inputs)?

2007-09-27 06:10:13 · 2 answers · asked by LG 7