Physics - October 2007

2007-10-15 12:46:41 · 7 answers · asked by erson j 1

A force of 105 N is applied horizontally to a 20.0 kg box to move it across a horizontal floor. If the box has an acceleration of 3.00m/s^2, find the coefficient of friction.

I know F=ma is used somehow, but where do I use it? Help please!

2007-10-15 12:44:20 · 2 answers · asked by Anonymous

A wheel turns through 5 revolutions while being accelerated from rest at 19 rpm/s.

What is the final angular speed?

How long does it take to turn the 5 revolutions?

2007-10-15 12:41:57 · 1 answers · asked by Nathan R 1

A buddy of mine told me it was pretty much impossible to be in the air for 1 second starting at the moment both feet leave the surface then reconnect. Is there any truth to this? It seems feasable to me.

2007-10-15 12:37:19 · 1 answers · asked by Anonymous

You are standing at the top of a cli® that has
a stairstep con¯guration. There is a vertical
drop of 5 m at your feet, then a horizontal
shelf of 8 m; then another drop of 5 m to the
bottom of the canyon, which has a horizontal
°oor. You kick a 0:43 kg rock, giving it an
initial horizontal velocity that barely clears
the shelf below. The acceleration of gravity is
9:8 m=s2 : Consider air friction to be negligi-
ble.



How far from the bottom of the second cli®
¢x will the projectile land? Answer in units
of m.

2007-10-15 12:21:18 · 1 answers · asked by dojorno5 2

A ball of mass 0:4 kg, initially at rest, is
kicked directly toward a fence from a point
20 m away, as shown below.
The velocity of the ball as it leaves the
kicker's foot is 17 m=s at angle of 51 ± above
the horizontal. The top of the fence is 7 m
high. The kicker's foot is in contact with the
ball for 0:04 s. The ball hits nothing while in
°ight and air resistance is negligible.
The acceleration due to gravity is 9:8 m=s2




What is the vertical component of the velocity
when the ball reaches the plane of the fence?
Answer in units of m=s.

2007-10-15 12:19:02 · 1 answers · asked by dojorno5 2

Ok...here's the problem. Person A has an egg and is standing at the top of a set of bleachers. Person B is walking at a constant rate past these bleachers. The objective is for Person A to drop the egg at a certain point so that it successfully hits Person B. What relationships should I be looking at mathematically? How would I go about developing a procedure in figuring out how to perform this with success?

I'm guessing this is just basic physics...I know some kinematics equations that might be used, but I'm not sure.

Thank you in advance for any help.

2007-10-15 12:10:22 · 2 answers · asked by Anonymous

I need to name a machine that doesnt use batteries, electricity, kinetic energy or an other energy

2007-10-15 11:45:12 · 5 answers · asked by Anonymous

A ball is thrown upward. Its initial vertical speed is 8.4 m/s, acceleration due to gravity is 9.8 m/s/s.
What is its maximum height reached? Answer in units of m.

2007-10-15 11:40:01 · 6 answers · asked by Zubin S 1

2007-10-15 11:36:31 · 2 answers · asked by Anonymous

You have two plates of copper, a sheet of mica (thickness = 0.10 mm, k = 5.4), a sheet of glass (thickness = 2.0 mm, k = 7.0), and a slab of paraffin (thickness = 1.0 cm, k = 2.0). To make a parallel-plate capacitor with the largest C, which sheet should you place between the copper plates?

2007-10-15 11:32:00 · 2 answers · asked by KwadwoT 1

W=?

original text of problem:
How much work is done by an Olympic triathlete who accelerates herself on her bicycle (a combined mass of 105kg) from 5.0 m/s to 10.0 m/s?

2007-10-15 11:24:49 · 3 answers · asked by S D 2

A 3.08 kg block starts from rest at the top of a 30° incline and accelerates uniformly down the incline, moving 2.28 m in 1.60 s.

Find the magnitude of the acceleration of the block.

Find the coefficient of kinetic friction between the block and the incline.

Find the magnitude of the frictional force acting on the block.

Find the speed of the block after it has slid a distance 2.28 m.

2007-10-15 10:59:09 · 1 answers · asked by John L 1

i need helpp withh this. what does each of these things do on a microscope?


ocular-
nosepiece-
objectives-
fine adjustment knob-
mirror or illuminator-

pllleeasee heelpp!

thankss SO much in advancce

2007-10-15 10:41:17 · 1 answers · asked by Anonymous

(a) At the end of this interval, what is the shaft's angular speed?

(b) What is the angle through which the shaft has turned?

2007-10-15 10:37:30 · 3 answers · asked by Anonymous

will she land?

2007-10-15 10:34:41 · 1 answers · asked by Shawn Carter 1

I know the answers but not how to get them. Here is the question:

A 40kg plank 6.0m long is supported by sawhorses A and B. A 60kg crate is placed on the plank, 2.0m from B.
(a) Find the reaction forces at A and B
(b) If the box is moved 1.0m closer to A and samhorse B is moved in 1.5m, find the reaction forces at A and B.

2007-10-15 10:18:14 · 2 answers · asked by ABC man 1

2007-10-15 10:02:36 · 5 answers · asked by kiran k 1

Assume natural gas with an energy content of 180,000J is burned, and the energy is used to warm water in a pan on the stove. If the energy of the water increases by 70,000J, determine the efficiency of the transfer.

2007-10-15 10:02:09 · 1 answers · asked by mheg 1

A certain spring is extended from x=0 to x=4 cm. It was previously found that a force of 70 Nt was required to extend the spring from x=0 to x=2 cm. How much work is done?

2007-10-15 10:00:29 · 1 answers · asked by mheg 1

driving at 30 m/s susan enters a one-lane tunnel, and
155 m ahead of her, a van is going at 5 m/s
she deaccelerates at -2 m/s
1. will there be a collision?
2. if so determine how far into the tunnel it will be and at what time it occurs
3. if not determine the distance between susan and the van

please show all work and use one of the five kinematics acceleration equations..thanks!!!

2007-10-15 09:56:59 · 2 answers · asked by Adam J 1

a speeding car is traveling at 92 km/h towards a police car at rest, facing the same direction as the speeding car. If cop car begins accelerating when speeding car is 250 m behind the cop car,then what must the cop car's acceleration be in order for the cop car to reach the speeding car's velocity at the moment the speeding car catches up? Assume that the speeding car doesn't slow down.

Please show all work necessary; Use one of the five kinematics equations...thanks!!!

2007-10-15 09:50:26 · 2 answers · asked by Adam J 1

A current of 86mA exists in a metal wire. How many electrons flow past a given cross-section of the wire in 10.1 min?

Thanks for your help!

2007-10-15 09:46:40 · 3 answers · asked by red58 1

A window washer drops a brush from a scaf-
fold on a tall office building.
The acceleration of gravity is 9.8 m/s2 :
What is the speed of the falling brush after
1.51 s? ( Neglect drag forces.) Answer in
units of m/s.

How far has it fallen in that time? Answer in
units of m.

2007-10-15 09:20:41 · 1 answers · asked by Sarah B 1

two small blocks, each of mass, m, are connected by a string of constant length, 4h and negligible mass. Block A is placed on a smooth tabletop and block B hangs over the edge of the table. The table top is a distance of 2h above of the floor. Block A is then released from rest at a distance h above the floor at time t=0. Express all algebraic answers in terms of h, m, and g.

a). Determine the acceleration of block B as it descends.
b. Block B strikes the floor and does not bounce. Determine the time t1, at which block b strikes the floor
c). Describe the motion of block A from time t=0 to the time when block B strikes the floor
d). Describe the motion of block a from the time block b strikes the floor to the time block a leaves the table
e). determine the distance between the landing points of the two blocks

2007-10-15 09:20:03 · 2 answers · asked by Mika 2

block and the surface is .26. A horizontal force F is applied to the 7.29 kg block. The acceleration of gravity is 9.8 m/s/s. Calculate the magnitude of the forces necessary to pull both blocks to the right with an acceleration of 1.71 m/s/s. Assume no slipping between the two blocks. Answer in units of N.

2007-10-15 09:14:35 · 1 answers · asked by sexysaraxx 4

A.slightly less

B. much less

C. slightly greater

D. the same

2007-10-15 09:06:50 · 4 answers · asked by cuerpito_15 1

2007-10-15 09:01:58 · 1 answers · asked by navya 1

farmhand attaches a 25 Kg bale of hay to one end of a rope passing over a frictionals pulley connected to a beam in the hay barn.then another farmhand pulls down on the opposite end of the rope with force of 277N. ignoring the mass of the rope, find the magntuide and dirction, gravitional force is 245N.

2007-10-15 09:01:03 · 1 answers · asked by big daddy 2

A ball is thrown straight up with an initial
speed of 70 m/s.
How high does it go? Assume the accelera-
tion of gravity is 10 m/s2 : Answer in units of
m.

How long is it in the air? Answer in units of
s.

2007-10-15 09:00:51 · 1 answers · asked by Sarah B 1