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Orlov [11]
3 years ago
12

A girl coasts down a hill on a sled, reaching

Physics
1 answer:
Simora [160]3 years ago
8 0

The sled travels a distance of 60.2 m before coming to rest.

The girl  reaches the ground with a speed <em>u</em>. She then travels forward on the hard icy snow, which has a coefficient of kinetic friction \mu _k . She comes to rest after travelling a distance <em>s</em> on the ground, due to the friction between the sled and the ground.

If the force of friction is <em>f</em> , the mass of the girl and the sled is <em>m</em> and the acceleration due to gravity is <em>g</em>, then,

f=\mu_kmg    .......(1)

This force exerts a decelerating force on the sled. If the deceleration of the sled is <em>a</em>, then,

f=ma   .......(2)

From equations (1) and (2),

f=\mu_kmg=-ma\\ a=-\mu_kg......(3)

Substitute 0.038 for  \mu _k and 9.81 m/s²for g.

a=-\mu_kg\\ =-(0.038)(9.81m/s^2)\\ =-0.3728m/s^2

Since the girl comes to rest, its final velocity is 0. Substitute 6.7 m/s for <em>u</em> and -0.3728m/s² for <em>a</em> in the equation of motion

v^2=u^2+2as

Solve for <em>s</em>.

v^2=u^2+2as\\ (0m/s)^2=(6.7m/s)^2+2(-0.3728m/s^2)s\\ s=\frac{(6.7m/s)^2}{2(0.3728m/s^2)} \\ =60.2m

Thus, the girl travels a distance of 60.2 m before coming to rest.

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kirza4 [7]

Answer:

The correct answer will be "-\frac{6C_{6}}{x^{7}}". The further explanation is given below.

Explanation:

The potential energy will be,

⇒  U(x)= -\frac{C_{6}}{x^6}

The expression of force will be,

⇒  F=-\frac{dU(x)}{dx}

⇒      =-(C_{6}(-6)x^{-7})

⇒      =-\frac{6C_{6}}{x^{7}}

Force seems to be appealing because the expression has been negative. It therefore means that the force or substance is acting laterally in on itself.

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3 years ago
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Explanation:

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Two waves can travel at the same speed, or even have the same wavelength, but this is not enough to be sure that at a given point in time, both waves will be in their maximum, as it only can be determined from the phase of the waves.

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If two objects A and B have the same kinetic energy but A has three times the momentum of B, what is the ratio of their inertias
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Answer:

\frac{inertia_B}{inertia_A}=9

Explanation:

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- The momentum of an object is given by p=mv

- The inertia of an object is proportional to its mass, so we can write I=km, where k just indicates a constant of proportionality

In this problem, we have:

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Re-writing both equation we have:

\frac{1}{2}m_A v_A^2 = \frac{1}{2}m_B v_B^2\\m_A v_A = 3 m_B v_B

If we divide first equation by second one we get

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m_A (3 v_B)^2 = m_B v_B^2\\9 m_A v_B^2 = m_B v_B^2\\m_B = 9 m_A

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