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inna [77]
3 years ago
5

Katelyn (55 kg) is practicing a drop jump in the biomechanics lab. She steps off a plyometrics box, lands on the force plate, an

d immediately jumps back up into the air. Right before she hits the force plate, her vertical velocity is 3.0 m/s downwards. After leaving the ground again, her vertical velocity is 3.5 m/s upwards. Katelyn was in contact with the ground for 0.4 seconds. (a) What was the impulse exerted on Katelyn when she was on the force plate
Physics
1 answer:
suter [353]3 years ago
5 0

Answer:

J = 357.5 kg*m/s

Explanation:

  • The impulse exerted on Katelyn when she was on the force plate, is equal to the change in her momentum, according to Newton's 2nd Law.
  • Assuming as the positive direction the upward direction (coincident with the positive y-axis) we can express the initial momentum as follows:

       p_{o} = m*v_{o} = 55 kg * (-3.0 m/s)  (1)

  • By the same token, the final momentum is as follows:

       p_{f} = m*v_{f} = 55 kg * (3.5 m/s)  (2)

  • As we have already said, the impulse J is just equal to the change in momentum, i.e., the difference between (2) and (1):

      J = p_{f} - p_{o} = m* (v_{f} -v_{o}) = 55 kg* (3.5m/s- (-3.0m/s)) = 357.5 kg*m/s (3)

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kakasveta [241]
<h2><u>Answers:</u></h2><h2>1.) Right answer: polarization  </h2>

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This is possible because electromagnetic waves are transversal waves, this means the electric field oscillates in all normal directions to the direction of wave propagation.

In other words:

<em>Its oscillation occurs in the transversal direction to its propagation. </em>

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It should be noted that this phenomenon is only possible in transversal waves, in longitudinal waves, such as sound waves, polarization is not possible because its oscillation occurs in the same direction as its propagation.

<h2>2.) Right answer: concave  </h2>

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A concave mirror, or convergent mirror, has a reflective surface that is curved inwards.

The concave mirrors reflect the light making it converge in a focal point therefore they are used to focus the light. This occurs because the light is reflected with different angles, since the normal to the surface varies from one point to another of the mirror.

<h2>3.) Right answer: photoelectric effect </h2>

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Light can be considered as a wave or as particles (photons), in this context the photoelectric effect can only be explained based on the corpuscular model (particles) of light.

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If the light is a stream of photons and each of them has energy, this energy is be able to pull an electron out of the crystalline lattice of the metal and communicate, in addition, a kinetic energy.

 

<h2>4.) Right answer: Taylor's experiment   </h2>

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This experiment was carried out by Geoffrey Taylor in 1909 with a flame as a light source, a diffraction grating and a photographic plate.

All this to test the diffraction of light.


<h2> 5.) Right answer: reflection  </h2>

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Mirrors fulfill the principle of reflection, which occurs when the light rays fall on a very flat reflecting surface are reflected so that the incident angle is equal to the reflected angle

<h2>6.) Right answer: mirage  </h2>

image of the sky seen on a hot road: mirage

A mirage is the product of an optical illusion due to the total reflection of the light when crossing layers of hot air of different density; this causes the perception of the inverted image of distant objects, as if they were reflected in the water.

<h2>7.) Right answer: virtual  </h2>

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<h2>8.) Right answer: diffraction  </h2>

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<h2>9.) Right answer: convex  </h2>

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A convex lens is thicker in the center than at its edges and concentrates (converges) at a point the rays of light that pass through it.

<h2>10.) Right answer: dispersion  </h2>

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The dispersion of light occurs when a beam of composite light is refracted (the different rays of light are diverted depending on their frequencies) in some medium, leaving their constituent colors separated.

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8 0
3 years ago
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A child in a boat throws a 5.80-kg package out horizontally with a speed of 10.0 m/s. The mass of the child is 24.6kg and the ma
Sergio [31]

Answer:

-0.912 m/s

Explanation:

When the package is thrown out, momentum is conserved. The total momentum after is the same as the total momentum before, which is 0, since the boat was initially at rest.

(m_c + m_b)v_b + m_pv_p = 0

where m_c = 24.6 kg, m_b = 39 kg, m_p = 5.8 kg are the mass of the child, the boat and the package, respectively. , v_p = 10m/s, v_b are the velocity of the package and the boat after throwing.

(24.6 + 39)v_b + 5.8*10 = 0

63.6v_b + 58 = 0

v_b = -58/63.6 = -0.912 m/s

3 0
3 years ago
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