Your Questions About Directions

Nagesh answers:

The sketch below represents a skater moving in a circular path at a constant speed in the direction indicated by the arrow.
(http://i56.tinypic.com/2qd03t5.gif)

Using numerical compass headings, determine the direction of the centripetal acceleration, centripetal force, and instantaneous velocity for the skater when at point X. Give acceleration direction, then force direction, then velocity direction.

As the skater moves around the circle, the skater is always leaning toward the center of the circle. The picture shows the skater moving clockwise around the circle, so the skater’s left foot is always exerting a force on the ice in the direction that is away from the center of the circle.
According to Newton’s 3rd law, the ice exerts a force on the skater of equal magnitude, but in the opposite direction. This causes the skater to move in a circular path.

If the skater was not leaning toward the center of the circle and exerting a force on the ice in the direction that is away from the center of the circle, the skater would move in a straight line that is tangent to the circle.

Each second, the skater moves on a line that is tangent to the circle, and each second this force causes the skater to move toward the center of the circle. The result of the tangential velocity and the radial force is circular motion.

The force is toward the center, so the acceleration is toward the center.
In the picture the direction of the centripetal force and the centripetal acceleration is South = 180°

The tangential velocity at Point X is pointing East, so the direction of the instantaneous velocity is East = 90°
Acceleration = South = 180°
Force = South = 180°
Velocity = 90° East

Nagesh answers:

Wind direction indicates from what direction the wind is coming from. A “Norther” is coming from the north. A “westerly” wind comes from the west, etc.

Nagesh answers:

One Direction is nothing more than a modern day Back Street Boys/New Kids On The Block singing group with below average to average singing ability and absolutely zero talent at writing songs and playing any instruments!

One Direction is just another “Sh_t Stain On The Underwear Of Music” soon to be forgotten answer to a trivia question that no one knows the answer to singing group!

Nagesh answers:

Hello Octavia

There is a rule in Physics called the “Right Hand Rule” .
Imagine that you point the thumb of your right hand along the wire and towards the North and grip the wire in the palm of your hand.Then your fingers will indicate the direction of the Magnetic field. It circles around above the wire from West to East and back around underneath the wire from East to West.

In a mind experiment if you imagine getting several different diameter tubes shaped like a toilet roll and putting them one inside the other with the wire through the centre of the tubes. The cylinders represent the magnetic field space around the wire.

Now, continuing with the mind experiment if you were to push a knitting needle up thrrough the cylinders from North to South, you could do that without puncturing through any tubes so there will be no resulting force travelling along the wire. The needle would fit between the tubes. But, if you poke the knitting needle through the tubes (From West to East) you will poke it through the tubes or force lines. The same amount of tubes would be penetrated if you poked it through in an upwards direction towards the sky, or downwards towards the floor.

Therefore the maximum magnetic force is in the direction West- East (or East to West) which is exactly the same as the upwards or downwards direction, rather than North to South (or South North).

There is anther way to prove this using vectors. But it involves surface intgrals and vector cross and dot products which are harder to describe so I hope the answer above is sufficient.

Tony

Nagesh answers:

.Since the charge of electron is 1.6×10^ -19 C the force exerted on it is: F = Eq = 3400×1.6×10^ -19 = 5.44×10^ -16 N if q is positive the force is in the same direction as the field. If q is negative the force and the field are in opposite directions. So the electric force opposite directions. So the electric force due west.