-What can you say about the snowboarder’s kinetic energy as he moves?

Physics

1 answer:

Damm [24]3 years ago

7 0

Answer:

His kinetic energy increases, potential energy decreases

The sum of kinetic and potential energy is a constant at any instant before he comes to rest.

Explanation:

Snowboarder is starting from a height and moving to the down direction. As he moves down his velocity increases, we know that kinetic energy is given by the expression $\frac{1}{2} mv^2$ , so as he moves his kinetic energy increases.

When the snowboarder is starting his potential energy is maximum(Potential energy = mgh), as he comes down his potential energy decreases.

Based on this we can conclude that the sum of potential energy and kinetic energy is a constant at any instant for a snowboarder before he comes to rest.

mgh+ $\frac{1}{2} mv^2$ = Constant

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An airplane of mass 1.60 ✕ 104 kg is moving at 66.0 m/s. The pilot then increases the engine's thrust to 7.70 ✕ 104 N. The resis

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(a) No, because the mechanical energy is not conserved

Explanation:

The work-energy theorem states that the work done by the engine on the airplane is equal to the gain in kinetic energy of the plane:

$W=\Delta K$ (1)

However, this theorem is only valid if there are no non-conservative forces acting on the plane. However, in this case there is air resistance acting on the plane: this means that the work-energy theorem is no longer valid, because the mechanical energy is not conserved.

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$W=\Delta K + E_{lost}$

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$F=7.70\cdot 10^4 N - 5.00 \cdot 10^4 N=2.70\cdot 10^4 N$