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3 years ago

Using evidence from the article, defend the concept that Earth’s magnetic poles have swapped places over time.

1 answer:

6 0

Answer: Scientists found evidence of Earths magnetic field reversal in rocks on the ocean floor at plate boundaries. These rocks have alternating polarity due to magnetization that occurred during their cooling period. Using radio metric dating, scientist estimate that reversals occur approximately every several hundred thousand years.

Explanation:

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What are the chances that radio transmissions from Earth or messages sent on distant space probes will ever be received by livin

spin [16.1K]

Answer:

<u>Explanation:</u>

It is fair to say to a reasonable extent that there are very low chances that radio transmissions from Earth or messages sent on distant space probes will ever be received by living beings .

Bear in mind that for years some scientists have believed without any substantial evidence that there are other living beings in distant space.

4 0

3 years ago

3. If a car is moving at 90km/hr and it rounds a corner, also at 90km/hr. Does it maintain

dolphi86 [110]

Answer:

Constant speed: yes

Constant velocity: no

Explanation:

Let's remind the definition of speed and velocity:

- Speed is a scalar quantity, which is equal to the ratio between the distance covered (regardless of the direction) and the time taken:

$s=\frac{d}{t}$

- Velocity is a vector quantity, so it has both a magnitude and a direction. The magnitude is equal to the rate between the displacement of the object and the time taken, while the direction is the same as the displacement.

In this problem, we notice that:

- The speed of the car remains constant, as it is 90 km/h

- However, its direction of motion changes while the car travels round the corner: this means that the direction of the velocity is also changing, therefore velocity is not constant.

8 0

3 years ago

A 10 kg monkey climbs up a massless rope that runs over a frictionless tree limb and back down to a 15 kg package on the ground.

pshichka [43]

Answer:

A. 4,9 m/s2

B. 2,0 m/s2

C. 120 N

Explanation:

In the image, 1 is going to represent the monkey and 2 is going to be the package. Let a_mín be the minimum acceleration that the monkey should have in the upward direction, so the package is barely lifted. Apply Newton’s second law of motion:

$\sum F_y=m_1*a_m_i_n = T-m_1*g$

If the package is barely lifted, that means that T=m_2*g; then:

$\sum F_y =m_1*a_m_i_n=m_2*g-m_1*g$

Solving the equation for a_mín, we have:

$a_m_i_n=((m_2-m_1)/m_1)*g = ((15kg-10kg)/10kg)*9,8 m/s^2 =4,9 m/s^2$

Once the monkey stops its climb and holds onto the rope, we set the equation of Newton’s second law as it follows:

For the monkey: $\sum F_y = m_1*a \rightarrow T-m_1*g=m_1*a$

For the package: $\sum F_y = m_2*a \rightarrow m_2*g - T = m_2*a$

The acceleration a is the same for both monkey and package, but have opposite directions, this means that when the monkey accelerates upwards, the package does it downwards and vice versa. Therefore, the acceleration a on the equation for the package is negative; however, if we invert the signs on the sum of forces, it has the same effect. To be clearer:

For the package: $\sum F_y = -m_2*a \rightarrow T-m2*g=-m_2*a \rightarrow m_2*g -T=m_2 *a$

We have two unknowns and two equations, so we can proceed. We can match both tensions and have:

$m_1*a+m_1*g=m_2*g-m_2*a$

Solving a, we have

$(m_1+m_2)*a =(m_2 - m1)*g\\\\a=((m_2-m_1)/(m_1+m_2))*g \rightarrow a=((15kg-10kg)/(10kg+15kg))*9,8 m/s^2\\\\a= 2,0 m/s^2$

We can then replace this value of a in one for the sums of force and find the tension T:

$T = m_1*a+m_1*g \rightarrow T=m_1*(a+g)\\\\T = 10kg*(2,0 m/s^2+9,8 m/s^2) \\\\T = 120 N$

5 0

3 years ago

Suppose a ball had a potential energy of 5 J when you dropped it.What would be it’s kinetic energy just as it hit the ground?

timama [110]

Answer:

Due to Conservation of Energy just as the ball hits the ground it's potential energy is assumed zero

Therefore disregarding air resistance all energy is converted into potential energy.

So KE = PE

(5 J)

4 0

2 years ago

How much physical activity do adults need

Irina18 [472]

For most healthy adults, the Department of Health and Human Services recommends these exercise guidelines: Aerobic activity. Get at least 150 minutes a week of moderate aerobic activity or 75 minutes a week of vigorous aerobic activity. You also can do a combination of moderate and vigorous activity.

5 0

3 years ago