Look it up on google it has the answer
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When you use a wrench to tighten or loosen a nut on a bolt, you are
applying torque. It is measured in units of force times distance.
A force of F newtons pulling on a handle of L meters in length would
supply a torque of F L newton-meters.
More technically, torque is the vector cross product of force times
perpendicular distance from the object, F x r = F r sin @
Answer:
a)

b) 
Explanation:
The net force on the car must produce the centripetal acceleration necessary to make this circle, which is
. At the top of the circle, the normal force and the weight point downwards (like the centripetal force should), while at the bottom the normal force points upwards (like the centripetal force should) and the weight downwards, so we have (taking the upwards direction as positive):

Which means:

The limit for falling off would be
, so the minimum speed would be:

Answer:

Explanation:
We define our values according to the text,
R= Radius
Velocity
Strenght of the vortex filament
From this and in a vectorial way we express an elemental lenght of this filmaent as
. So,

Where
imply a vector acting perpendicular to both vectors.
Applying Biot-Savart law, we have,

Substituting the preoviusly equation obtained,



So we can express the velocity induced is,
