I tried using 10^-10 as the power emitted (got that from a website) and this is what I did:
I= 10^-10/ 4pi*3^2
I= 8.8*10^-13
That was wrong, so I'm really at a loss here.
Homework Statement
What is the sound intensity of a whisper at a distance of 3.0 m, in W/m^2 ?
What is the corresponding sound intensity level in dB?
Homework Equations
I=P/4*pi*r^2
The Attempt at a Solution
I tried looking up what the power of a whisper was and I can't find...
oh! The equation I have for work is W=Fx, but all that is given to me is two velocities and a mass. Force is m*a so w=m*a*x. I guess I'm still at a loss here.
Homework Statement
A 55 g particle is moving to the left at 27 m/s. How much work must be done on the particle to cause it to move to the right at 41 m/s? Answer in joules
Homework Equations
The Attempt at a Solution
27-(-41)=68 , 68*55= 3750
the units here are grams m/s. I...
Homework Statement
A 1.4 kg book is lying on a 0.80 m-high table. You pick it up and place it on a bookshelf 2.2 m above the floor.
1) How much work does your hand do on the book?
2.) How much work does gravity do on the book? [solved]
Homework Equations
Force*displacement=work...
ok. The work energy theorem is basically saying that since energy is always conserved, something had to provide energy and its done through work. So in less words it is the relationship between the work done and the change in energy.
I think gravity is doing most of the work by pulling the...
Homework Statement
You are a member of an alpine rescue team and must get a box of supplies, with mass 2.20 kg, up an incline of constant slope angle 30.0 degrees so that it reaches a stranded skier who is a vertical distance 2.80 m above the bottom of the incline. There is some friction...
Honestly, I had no idea what I was doing. I tried looking at how someone solved the same problem with different numbers and just plugged my numbers in but it didn't work.
Homework Statement
A 4.6×104 kg locomotive, with steel wheels, is traveling at 14 m/s on steel rails when its engine and brakes both fail. The coefficient of friction is 1.6×10−3.
1.) How far will the locomotive roll before it comes to a stop?
Answer in meters using two significant...
Quick question about forces!!!
Homework Statement
A skier is sliding down a 15 degree slope. Friction is not negligible. Identify all forces on the skier.
Homework Equations
n/a
The Attempt at a Solution
The choices are: Tension, Kinetic Friction, Weight, Static Friction...
Homework Statement
Blocks with masses of 4.0 kg, 8.0 kg, and 9.0 kg are lined up in a row on a frictionless table. All three are pushed forward by a 15 N force applied to the 4.0 kg block.
1.) How much force does the 8.0 kg block exert on the 9.0 kg block?
2.)How much force does the...
Homework Statement
A 20 kg loudspeaker is suspended 2.5 m below the ceiling by two cables that are each 20 degrees from vertical. What is the tension the cables?
Homework Equations
The Attempt at a Solution
I have no idea on what equation to use, considering we haven't even...
Homework Statement
A position vector in the first quadrant has an x-component of 6.0m and a magnitude of 10m
What is the value of its y-component?
Homework Equations
?
The Attempt at a Solution
Well I originally thought I could draw a graph where x=6 and y=...then I realized i...
Ok. Maybe I'm doing calculations wrong, but I got 27 and MasteringPhysics says that is wrong. Here is what I did:
v2=vo2+2ax
0=vo2+(2*-12)(31) 31 is 39-8, and .5*16=8
0=vo2+(-744)
squared root of 744=Vo
Vo=27
Where did I go wrong?
I understand what the problem is saying, I just don't know how to find the answer. I don't know what equation to use or how to even go about solving it.
I've already solved the first part of the problem. There are 20 meters between me and the deer. I'm just not sure about the other part. What is the maximum speed you could have and still not hit the deer?
Homework Statement
You're driving down the highway late one night at 16 m/s when a deer steps onto the road 39 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 12 m/s^2 . How much distance is between you and the...
Homework Statement
A rock is tossed straight up with a speed of 21 m/s. When it returns, it falls into a hole 15 m deep. What is the rock's velocity as it hits the bottom of the hole? How long is the rock in the air, from the instant it is released until it hits the bottom of the hole...