What is true about energy that is added to a closed system

Since the coefficient of friction is less than 1, what does that mean about the normal force and the force of friction?

ludmilkaskok [199]

Answer:

there is friction between the two things

Explanation:

7 0

3 years ago

A bird lands on a bare copper wire carrying a current of 51

nirvana33 [79]

The resistance of the piece of wire is
$R= \frac{\rho L}{A}$
where
$\rho = 1.68 \cdot 10^{-8}\Omega m$ is the resistivity of the copper
$L=5.1 cm=0.051 m$ is the length of the piece of wire
$A=0.13 cm^2 = 0.13 \cdot 10^{-4} m^2$ is the cross sectional area of the wire
By substituting these values, we find the value of R:
$R= \frac{\rho L}{A}=6.6 \cdot 10^{-5} \Omega$

Then, by using Ohm's law, we find the potential difference between the two points of the wire:
$V=IR=(51 A)(6.6 \cdot 10^{-5} \Omega )=3.4 \cdot 10^{-3} V$

7 0

3 years ago

A playground slide is in the form of an arc of a circle with a maximum height of 3.0 m, with a radius of 8.5 m, and with the gro

julia-pushkina [17]

Answer:

a) $s \approx 6.676\,m$

Explanation:

a) Let assume that the ground is not inclined, since the bottom of the playground slide is tangent to ground. Then, the length of given by the definition of a circular arc:

$s = \frac{\pi}{4}\cdot R$

$s=\frac{\pi}{4}\cdot (8.5\,m)$

$s \approx 6.676\,m$

The bottom of the slide has a height of zero. The physical phenomenon around Dr. Ritchey's daughter is modelled after Principle of Energy Conservation. The child begins at rest:

$U_{g,A} = K_{B} + W_{fr}$

$m\cdot g \cdot h_{A} = \frac{1}{2}\cdot m \cdot v_{B}^{2} + f\cdot s$

The average frictional force is cleared within the expression:

$f = \frac{m\cdot (g\cdot h_{A}-\frac{1}{2}\cdot v_{B}^{2})}{s}$

$f = \frac{(12\,kg)\cdot [(9.807\,\frac{m}{s^{2}} )\cdot (3\,m)-\frac{1}{2}\cdot (4.5\,\frac{m}{s} )^{2} ]}{6.676\,m}$

$f = 34.684\,N$

4 0

3 years ago

A string is 1.6 m long. One side of the string is attached to a force sensor and the other side is attached to a ball with a mas

Sergio039 [100]

Complete Question

The diagram for this question is shown on the first uploaded image

Answer:

The distance traveled in horizontal direction is $D = 1.38 m$

Explanation:

From the question we are told that

The length of the string is $L = 1.6 \ m$

The mass of the ball is $m = 200 g = \frac{200}{1000} = 0.2 \ kg$

The height of ball is $h = 1.5 \ m$

Generally the work energy theorem can be mathematically represented as

$PE = KE$

Where PE is the loss in potential energy which is mathematically represented as

$PE =mgh$

Where h is the difference height of ball at A and at B which is mathematically represented as

$h = y_A - y_B$

So $PE =mg(y_A - y_B)$

While KE is the gain in kinetic energy which is mathematically represented as

$KE = \frac{1}{2 } (v_b ^2 - 0)$

Where $v_b$ is the velocity of the of the ball

Therefore we have from above that

$PE =KE \equiv mg (y_A - y_B) = \frac{1}{2} m (v_b ^2 - 0)$

Making $v_b$ the subject we have

$v_b = \sqrt{2g (y_A - y_B)}$

substituting values

$v_b = \sqrt{2g (1.5 - 0.40)}$

$v_b = 4.6 \ m/s$

Considering velocity of the ball when it hits the floor in terms of its vertical and horizontal component we have

$v_x = 4.6 m/s \ while \ v_y = 0 m/s$

The time taken to travel vertically from the point the ball broke loose can be obtained using the equation of motion

$s = v_y t - \frac{1}{2} g t^2$

Where s is distance traveled vertically which given in the diagram as $s = -0.4$

The negative sign is because it is moving downward

Substituting values

$-0.4 = 0 -\frac{1}{2} * 9.8 * t^2$

solving for t we have

$t = 0.3 \ sec$

Now the distance traveled on the horizontal is mathematically evaluated as

$D = v_b * t$

$D = 4.6 * 0.3$

$D = 1.38 m$

8 0

3 years ago

How is a dam used to generate electric energy?

Alexxandr [17]

Answer:

Hydroelectric

Explanation:

Hydroelectric energy is usually generated by constructing a dam on a river, such that the water which flows through the dam is used to power turbines that generate electricity.

The quantity of energy that can be generated depends on the volume of water available and the difference in height between the water’s source and its outflow.

5 0

3 years ago

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