A rock is thrown across a frozen pond with an initial speed of 8m/s. Which statement best describes the motion of the rock?

Physics

1 answer:

olga55 [171]3 years ago

7 0

Answer:

Option C: "The rock will slow down and eventually stop"

Explanation:

Since this is a real event, and not an ideal situation where there is no friction forces acting between the frozen pond and the rock, there is going to exist some force of dynamic friction (even small) acting between them. One can look up coefficients of dynamic friction between similar objects, and realize that some small force will be acting as the rock slides on the surface of the pond. That force acts always opposite the direction of movement, therefore decelerating the rock. The rock's speed will continue reducing in magnitude until it eventually stops.

Then, the selected answer is: "The rock will slow down and eventually stop."

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castortr0y [4]

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3 years ago

The 8 kg block is then released and accelerates to the right, toward the 2 kg block. The surface is rough and the coefficient of

natita [175]

Answer:

3.258 m/s

Explanation:

k = Spring constant = 263 N/m (Assumed, as it is not given)

x = Displacement of spring = 0.7 m (Assumed, as it is not given)

$\mu$ = Coefficient of friction = 0.4

Energy stored in spring is given by

$U=\dfrac{1}{2}kx^2\\\Rightarrow U=\dfrac{1}{2}\times 263\times 0.7^2\\\Rightarrow U=64.435\ J$

As the energy in the system is conserved we have

$\dfrac{1}{2}mv^2=U-\mu mgx\\\Rightarrow v=\sqrt{2\dfrac{U-\mu mgx}{m}}\\\Rightarrow v=\sqrt{2\dfrac{64.435-0.4\times 8\times 9.81\times 0.7}{8}}\\\Rightarrow v=3.258\ m/s$