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On a loop the loop a ball of mass m starts from rest a distance 6 R above the table, where R is the radius of the loop. When the ball rolls without friction, at some instant it is right at the top of the loop, a distance of 2 R above the table. At this instant, with what force is it press ing against the track? 1. Zero 2. Because the ball is rolling, it can't exert a force on anything. 3. m g 4. The ball will not be in contact with the track at this point, since it does not have quite enough speed to reach it 5. 3 mg 6. 7m g 7. 2m g 8. 5 m g 9. 6 mg 10. 4 mg

Respuesta :

By energy conservation:

[tex]\frac{1}{2}mv_a^2 + mgH = \frac{1}{2}mv_b^2 + mgh[/tex]

[tex]\frac{1}{2}m*0^2 + mg*6R = \frac{1}{2}mv_b^2 + mg*2R[/tex]

[tex]4gR = \frac{1}{2}v_b^2[/tex]

[tex]\sqrt{8gR }=v_b[/tex]

Now by force balance at the top point

[tex]mg + F_N = \frac{mv_b^2}{R}[/tex]

[tex]mg + F_N = \frac{m*8gR}{R}[/tex]

[tex]F_N = \frac{8mgR}{R} - mg[/tex]

[tex]F_N = 7 mg[/tex]

2. [tex]U =cr^2 - er^4[/tex]

Force and potential energy is related by the following equation

[tex]F = - \frac{dU}{dr}[/tex]

[tex]F = - \frac{d}{dr}cr^2 - er^4[/tex]

[tex]F = \hat r (- 2cr + 4er^3)[/tex].

Forces are influences that can change the movement of an object. A force can change the velocity of an object with mass accelerating it. Forces can also be described intuitively by pushing or pulling. A force has both magnitude and direction and is a vector quantity. The word force has a precise meaning.

Learn more about Force here:-https://brainly.com/question/12970081

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