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12345 [234]
3 years ago
5

On a cold day you can warm your hands by rubbing them together. (a) Assume that the coefficient of friction between your hands i

s 0.5, that the normal force between your hands is 34 N, and that you rub them together at an average speed of 30 cm/s. What is the rate at which heat is generated?
Physics
1 answer:
melomori [17]3 years ago
6 0

To solve this problem it is necessary to apply the equations related to the Force of Friction and Energy.

By definition the friction force is defined as

F= \mu * N

Where,

\mu = Frictional Constant

N = Normal Force -> mg

At the same time we have the definition of the Energy, which can be

E = F*v

Where,

Force

v = Velocity.

Then replacing with our values we have that,

F = \mu N

F = 0.5 *34

F = 17

The energy then would be,

E = f v

E = 17 * 0.30 = 5.1 W

Therefore the rate at which heat is generated is 5.1W

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A 2.0 kg particle moves in a circle of radius 3.1 m. As you look down on the plane of its orbit, the particle is initially movin
Ghella [55]

Answer

given,

L(t) = 10 - 3.5 t

mass of particle = 2 Kg

radius of the circle = 3.1 m

a) torque

    τ = \dfrac{dL}{dt}

    τ = \dfrac{d}{dt}(10 - 3.5 t)

    τ = -3.5 N.m

Particle rotates clockwise as i look down the plane. Hence, its angular velocity is downward.

L decreases the angular acceleration upward. so, net torque is upward.

b) Moment of inertia of the particle

    I = m R^2

    I = 2 x 3.1²

    I = 19.22 kg.m²

    L = I ω

    ω = \dfrac{L}{I}

    ω = \dfrac{10 - 3.5 t}{19.22}

    ω = 0.520 - 0.182 t

  A = 0.52 rad/s             B = -0.182 rad/s²

5 0
3 years ago
Read 2 more answers
A musical note has a frequency of 512 Hz. If the wavelength of the note is 0.685 m, what is the speed of the sound of that note?
riadik2000 [5.3K]

Answer:

350.72 m/s

Explanation:

Formula for velocity of wave is;

v = fλ

Where;

v is speed

f is frequency

λ is wavelength

We are given;

f = 512 Hz

λ = 0.685 m

Thus;

v = 512 × 0.685

v = 350.72 m/s

5 0
3 years ago
A city planner needs to make a model of the city. In real life, the tallest tree in the city is 40 feet tall. The shortest tree
Verdich [7]
To solve this you must set up what is called a proportion.  A proportion is a way of comparing two comparing values where one of the four values is missing.  In your problem the missing value is the height of the smallest tree in the model.

To set up a proportion, you need all of your values.  The easiest way to do this is to list them:

Highest tree in real life:  40ft
Highest tree in model:  10ft
Smallest tree in real life:  4ft
Smallest tree in model:  x

So know you can set your proportion like this:

40/4 = 4/x

(When setting up a proportion, you always want to have the values belong to each other.  For example don't put the height of the small tree in the model underneath the value of the highest tree in real life.)

So know to find what the x values equals, we need to cross multiply.  And then all that's left after that is to solve for x.

40 times x = 4 times 4

40x = 16

x = 2.5

The smallest tree in the model should equal 2.5 feet.

Hope this helps! :)



6 0
3 years ago
Student A states that when she sits down on a chair, she is exerting a force on the chair and that is all that happens. Student
zvonat [6]

Answer:

C

Explanation:

I got it right on the test !!

7 0
3 years ago
On the sonometer shown below, a horizontal cord of length 5 m has a mass of 1.45 g. When the cord was plucked the wave produced
Korolek [52]

Answer:

(a) T = 0.015 N

(b) M = 1.53 x 10⁻³ kg = 1.53 g

Explanation:

(a) T = 0.015 N

First, we will find the speed of waves:

v =f\lambda

where,

v = speed of wave = ?

f = frequency = 120 Hz

λ = wavelength = 6 cm = 0.06 m

Therefore,

v = (120 Hz)(0.06 m)

v = 7.2 m/s

Now, we will find the linear mass density of the coil:

\mu = \frac{m}{l}

where,

μ = linear mass density = ?

m = mass = 1.45 g = 1.45 x 10⁻³ kg

l = length = 5 m

Thereforre,

\mu = \frac{1.45\ x\ 10^{-3}\ kg}{5\ m}\\\\\mu = 2.9\ x\ 10^{-4}\ kg/m

Now, for the tension we use the formula:

v = \sqrt{\frac{T}{\mu}}\\\\7.2\ m/s = \sqrt{\frac{T}{2.9\ x\ 10^{-4}\ kg/m}}\\\\(51.84\ m^2/s^2)(2.9\ x\ 10^{-4}\ kg/m) = T

<u>T = 0.015 N</u>

<u></u>

(b)

The mass to be hung is:

T = Mg\\\\M = \frac{T}{g}\\\\M = \frac{0.015\ N}{9.8\ m/s^2}\\\\

<u>M = 1.53 x 10⁻³ kg = 1.53 g</u>

4 0
3 years ago
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