A force of 1.150×103 N pushes a man on a bicycle forward. Air resistance pushes against him with a force of 795 N. If he starts from rest and is on a level road, what speed ???? will he be going after 35.0 m? The mass of the bicyclist and his bicycle is 90.0 kg.

Respuesta :

Answer:

He has a speed of 16.60m/s after 35.0 meters.

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)

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)

All the forces can be easily represented in a free body diagram, as it is shown below.

Forces in the x axis:

[tex]F_{x} = F - F_{air}[/tex]  (3)

Forces in the y axis:

[tex]F_{y} = 0[/tex] (4)

Solving for the forces in the x axis:

[tex]F_{x} = F - F_{air}[/tex]

Where [tex]F = 1.150x10^{3} N[/tex] and [tex]F_{air} = 795 N[/tex]:

[tex]F_{x} = 1.150x10^{3} N - 795 N[/tex]

[tex]F_{x} = 355 N[/tex]

Replacing in equation (2) it is gotten:

[tex]Fx + Fy = ma[/tex]

[tex]355 N + 0 N = (90.0 Kg)a[/tex]

[tex]355 N = (90.0 Kg)a[/tex]

[tex]a = \frac{355 N}{90.0Kg}[/tex]

[tex]a = \frac{355 Kg.m/s^{2}}{90.0Kg}[/tex]

[tex]a = 3.94 m/s^{2}[/tex]

So the acceleration for the cyclist is [tex]3.94 m/s^{2}[/tex], now that the acceleration is known, equation (1) can be used:

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

However, since he was originally at rest its initial velocity will be zero ([tex]v_{i} = 0[/tex]).

[tex]v_{f} = \sqrt{2ad}[/tex]

[tex]v_{f} = \sqrt{2(3.94m/s^{2})(35.0m)}[/tex]

[tex]v_{f} = 16.60m/s[/tex]

He has a speed of 16.60m/s after 35.0 meters

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