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Shalnov [3]
3 years ago
8

When the displacement of a mass on a spring is 12 a the half of the amplitude, what fraction of the mechanical energy is kinetic

energy?
Physics
1 answer:
Sveta_85 [38]3 years ago
7 0
You know that when the displacement is equal to the amplitude (A), the velocity is zero, which implies that the kinetic energy (KE) is zeero, so the total mechanical energy (ME) is the potential energy (PE).

And you know that the potential energy, PE, is [ 1/2 ] k (x^2)

Then, use x = A, to calculate the PE in the point where ME = PE.

ME = PE = [1/2] k (A)^2.

At half of the amplitude, x = A/2 => PE = [ 1/2] k (A/2)^2

=> PE = [1/4] { [1/2]k(A)^2 } = .[1/4] ME

So, if PE is 1/4 of ME, KE is 3/4 of ME.

And the answer is 3/4


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4 0
2 years ago
A 0.75μF capacitor is charged to 70 V . It is then connected in series with a 55Ω resistor and a 140 Ω resistor and allowed to d
Ipatiy [6.2K]

Answer:

Explanation:

Capacitor of 0.75μF, charged to 70V and connect in series with 55Ω and 140 Ω to discharge.

Energy dissipates in 55Ω resistor is given by V²/R

Since the 55ohms and 140ohms l discharge the capacitor fully, the voltage will be zero volts and this voltage will be shared by the resistor in ratio.

So for 55ohms, using voltage divider rule

V=R1/(R1+R2) ×Vt

V=55/(55+140) ×70

V=19.74Volts is across the 55ohms resistor.

Then, energy loss will be

E=V²/R

E=19.74²/55

E=7.09J

7.09J of heat is dissipated by the 55ohms resistor

6 0
3 years ago
Two Polaroids are aligned so that the initially unpolarized light passing through them is a maximum. At what angle should one of
steposvetlana [31]

To solve this problem it is necessary to apply the law of Malus which describes the change in the Intensity of Light when it crosses a polarized surface.

Mathematically the expression is given as

I = I_0 cos^2\theta

Where,

I_0= Initial Intensity

I = Final Intensity after pass through the polarizer

\theta= Angle between the polarizer and the light

Since it is sought to reduce the intensity by half the relationship between the two intensities will be given as

\frac{I}{I_0} = \frac{1}{2}

Using the Malus Law we have,

I = I_0 cos^2\theta

cos^2\theta = \frac{I}{I_0}

cos^2\theta = \frac{1}{2}

\theta = cos^{-1}(\frac{1}{2})^2

\theta = 75.52\°

Angle with respect to maximum is 90-75.52 = 14.48\°

8 0
2 years ago
A car takes off from rest takes of from rest and covers a distance of 80m on a straight road in 10s.Calculate the magnitude of i
hodyreva [135]
  • Initial velocity (u) = 0 m/s [the car was at rest]
  • Distance (s) = 80 m
  • Time (t) = 10 s
  • Let the magnitude of acceleration be a.
  • By using the equation of motion, s = ut +  \frac{1}{2} a {t}^{2}we get,80 = 0 \times 10 +  \frac{1}{2}  \times a \times  {10}^{2}  \\  =  > 80 =  \frac{1}{2}  \times 100a \\  =  > 80 = 50a \\  =  > a =  \frac{80}{50}  \\  =  > a = 1.6

<u>A</u><u>nswer:</u>

<u>The </u><u>magnitude</u><u> </u><u>of </u><u>its </u><u>acceleration</u><u> </u><u>is </u><u>1</u><u>.</u><u>6</u><u> </u><u>m/</u><u>s^</u><u>2</u><u>.</u>

Hope you could get an idea from here.

Doubt clarification - use comment section.

4 0
2 years ago
Which force requires contact?
Minchanka [31]

Answer:

A

Explanation: A is a example of Air resistance force, which is a contact force.

8 0
3 years ago
Read 2 more answers
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