A student is skateboarding down a ramp that is 6.0 m long and inclined at 180 with respect to the horizontal. The initial speed of the skateboarder at the top of the ramp is 2.6 m/s. Neglect friction and find the speed at the bottom of the ramp.

Respuesta :

Answer:

The speed at the bottom of the ramp is 2.6m/s

Explanation:

The final velocity can be determined by means of the equations for a Uniformly Accelerated Rectilinear Motion:

[tex]v_{f}^{2} = v_{i}^{2} + 2ad[/tex]

[tex]v_{f} = \sqrt{v_{i}^{2} + 2ad}[/tex] (1)

Notice that it is necessary to found the acceleration that can be done by means of Newton's second law:

The acceleration can be found by means of Newton's second law:

[tex]\sum F_{net} = ma[/tex]

Where [tex]\sum F_{net}[/tex] is the net force, m is the mass and a is the acceleration.

[tex]Fx + Fy = ma[/tex] (2)

Force in the x axis:

[tex]F_{x} = W_{x}[/tex]  

The component of the weight in the x axis can be gotten by means of trigonometric:

[tex]\frac{OC}{H} = sen \theta[/tex]

[tex]\frac{W_{x}}{W} = sen \theta[/tex]

[tex]W_{x} = W sen \theta[/tex]

[tex]W_{x} = mgsen \theta[/tex]

[tex]F_{x} = mgsen \theta[/tex]  (3)

Forces in the y axis:

[tex]F_{y} = N - W_{y}[/tex] (4)

The component of the weight in the y axis can be gotten by means of trigonometric:

[tex]\frac{AC}{H} = cos \theta[/tex]

[tex]\frac{W_{y}}{W} = cos \theta[/tex]

[tex]W_{y}= W cos \theta[/tex]

Remember that the weight is defined as:

[tex]W = mg[/tex]

[tex]W_{y}= mgcos \theta[/tex]

The normal force can be obtained from equation (4)

[tex]N - W_{y} = 0[/tex]

[tex]N = W_{y}[/tex]

[tex]N = mgcos \theta[/tex]

Therefore, equation 4 can be rewritten as:

[tex]F_{y} = mgcos \theta - mgcos \theta[/tex]

[tex]F_{y} = 0[/tex] (5)

Then, replacing equation 3 and equation 5 in equation 2 it is gotten:

[tex]mgsen \theta + 0 = ma[/tex]

[tex]mgsen \theta = ma[/tex] (6)

However, a can be isolated from equation 6

[tex] a = \frac{mgsen \theta}{m}[/tex]

[tex] a = gsen \theta[/tex]  (7)

Finally, equation 7 can be replaced in equation 2:

[tex]v_{f} = \sqrt{v_{i}^{2} + 2d(gsen \theta)}[/tex]

[tex]v_{f} = \sqrt{(2.6m/s)^{2} + 2(6.0m)(9.8m/s^{2})sen 180^{\circ})}[/tex]

[tex]v_{f} = 2.6m/s[/tex]

Hence, the speed at the bottom of the ramp is 2.6m/s

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