# Direction of Force

You are riding on a Ferris wheel that is rotating with constant speed. The car in which you are riding always maintains its correct upward orientation; it does not invert.

http://www.webassign.net/pse/6-03.gif

What is the direction of the normal force on you from the seat when you are at the top of the wheel?

a)downward

b)upward

c)impossible to determine

What is the direction of the net force on you when you are at the top of the wheel?

a)downward

b)upward

c)impossible to determine

Consider a ball on a fixed-length string being whirled in a vertical circular path as shown in the diagram below.

http://www.webassign.net/waplots/6/c/8790d464a5932ce7c7734235eac44c.gif

http://www.webassign.net/waplots/f/1/b418102dcd1b0f934de2ce300a651e.gif

a)When the ball is at the bottom of the circle, what is the direction of the tension force on the ball? Use the direction rosette to answer this question.

1,2,3,4,5,6,7,8,or 9

b)When the ball is at the bottom of the circle, what is the direction of the gravitational force on the ball? Use the direction rosette to answer this question.

1,2,3,4,5,6,7,8,or 9

c) When the ball is at the bottom of the circle, what is the direction of the centripetal force on the ball? Use the direction rosette to answer this question.

1,2,3,4,5,6,7,8 or 9

d)When the ball is at the bottom of the circle, what is the expression for the centripetal force on the ball? Take the upward direction as positive and the downward direction as negative when considering the sign of the forces. (Use the following as necessary: m, g and T.)

e)If the speed of the ball at the bottom of the circle is v, what is the expression for the centripetal force on the ball in terms of its speed v and the length L of the string? Take the upward direction as positive and the downward direction as negative when considering the sign of the forces. (Use the following as necessary: m, v and L.)

f)Use your answers in parts (d) and (e) to get an expression for the tension in the string in terms of the speed of the ball and the length of the string. (Use the following as necessary: m, v, g and L.)