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3 years ago

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Which list of observations is the best evidence of only a chemical change occurring?

1 answer:

Aleonysh [2.5K]3 years ago

7 0

Answer:

d

Explanation:

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Suppose you first walk 12.0 m in a direction 20? west of north and then 20.0 m in a direction 40.0? south of west. how far are y

Gnesinka [82]

The representation of this problem is shown in Figure 1. So our goal is to find the vector $\overrightarrow{R}$ . From the figure we know that:

$\left | \overrightarrow{A} \right |=12m \\ \\ \left | \overrightarrow{B} \right |=20m \\ \\ \theta_{A}=20^{\circ} \\ \\ \theta_{B}=40^{\circ}$

From geometry, we know that:

$\overrightarrow{R}=\overrightarrow{A}+\overrightarrow{B}$

Then using vector decomposition into components:

$For \ A: \\ \\ A_x=-\left | \overrightarrow{A} \right |sin\theta_A=-12sin(20^{\circ})=-4.10 \\ \\ A_y=\left | \overrightarrow{A} \right |cos\theta_A=12cos(20^{\circ})=11.27 \\ \\ \\ For \ B: \\ \\ B_x=-\left | \overrightarrow{B} \right |cos\theta_B=-20cos(40^{\circ})=-15.32 \\ \\ B_y=-\left | \overrightarrow{B} \right |sin\theta_B=-20sin(40^{\circ})=-12.85$

Therefore:

$R_x=A_x+B_x=-4.10-15.32=-19.42m \\ \\ R_y=A_y+B_y=11.27-12.85=-1.58m$

So if you want to find out <span>how far are you from your starting point you need to know the magnitude of the vector $\overrightarrow{R}$ , that is:
</span>
$\left | \overrightarrow{R} \right |=
\sqrt{R_x^2+R_y^2}=\sqrt{(-19.42)^2+(-1.58)^2}=\boxed{19.48m}$

Finally, let's find the <span>compass direction of a line connecting your starting point to your final position. What we are looking for here is an angle that is shown in Figure 2 which is an angle defined with respect to the positive x-axis. Therefore:

</span> $\theta_R=180^{\circ}+tan^{-1}(\frac{\left | R_y \right |}{\left | R_x \right |}) \\ \\ \theta_R=180^{\circ}+tan^{-1}(\frac{1.58}{19.42}) \\ \\ \theta_R=180^{\circ}+4.65^{\circ}=185.85^{\circ}$

6 0

3 years ago

Which of the following is likely to contribute to geological events that take place on Earth?

Dennis_Churaev [7]

Crust sitting on top of Milton rock of the mantle

5 0

3 years ago

Read 2 more answers

The mass of the sun is 1.9891030 kg and the mass of the Earth is 5.9721024kg. If the Earth’s acceleration toward the sun is 0.00

saul85 [17]

Answer:

this is the answer according to my calculations

Explanation:

0.001.9

5 0

3 years ago

A spinning wheel has a rotational inertia of 2 kg•m². It has an angular velocity of 6.0 rad/s. An average counterclockwise torqu

ira [324]

Answer:

$-20.0 kg m^2/s$

Explanation:

The angular momentum of an object in rotation is given by

$L=I \omega$

where

I is the moment of inertia

$\omega$ is the angular speed

In this problem, initially we have

$I=2 kg m^2$ is the moment of inertia of the wheel

$\omega_i = 6.0 rad/s$ is the initial angular speed

So the initial angular momentum is

$L_i = I\omega_i = (2)(6.0)=12 kg m^2/s$

Later, a counterclockwise torque of

$\tau=-5.0 Nm$ is applied

So the angular acceleration of the wheel is:

$\alpha = \frac{\tau}{I}=\frac{-5.0}{2}=-2.5 rad/s^2$ in the direction opposite to the initial rotation.

As a result, the final angular velocity of the wheel will be:

$\omega_f = \omega_i + \alpha t$

where

t = 4.0 is the time interval

Solving,

$\omega_f = +6.0 +(-2.5)(4.0)=-4 rad/s$

which means that now the wheel is rotating in the counterclockwise direction.

Therefore, the new angular momentum of the wheel is:

$L_f = I\omega_f =(2)(-4.0)=-8.0 kg m^2/s$

So, the change in angular momentum is:

$\Delta L=L_f - L_i = (-8.0-(12))=-20.0 kg m/s^2$

7 0

3 years ago

A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but four times as long. If, however, the to

Elanso [62]

Answer:

E. two times the original diameter

Explanation:

Resistance of a wire is:

R = ρ L/A

where ρ is the resistivity of the material, L is the length, and A is the cross-sectional area.

For a round wire with diameter d:

R = ρ L / (¼ π d²)

The two wires must have the same resistance, so:

ρ₁ L₁ / (¼ π d₁²) = ρ₂ L₂ / (¼ π d₂²)

The wires are made of the same material, so ρ₁ = ρ₂:

L₁ / (¼ π d₁²) = L₂ / (¼ π d₂²)

The new length is four times the old, so 4 L₁ = L₂:

L₁ / (¼ π d₁²) = 4 L₁ / (¼ π d₂²)

1 / (¼ π d₁²) = 4 / (¼ π d₂²)

Solving:

1 / (d₁²) = 4 / (d₂²)

(d₂²) / (d₁²) = 4

(d₂ / d₁)² = 4

d₂ / d₁ = 2

So the new wire must have a diameter twice as large as the old wire.

3 0

3 years ago