Henrik finds an unlabeled diagram in his notes: a circle, a dot at its center, an object at the top, and two arrows at the object. One arrow lies on the circle's tangent; the other aims at the center.
Which arrow is which? And which way is the object going?
A finished uniform-circular-motion diagram shows two arrows at the object.
The arrow on the tangent at the object's position is the velocity.
The arrow aimed from the object at the circle's center is the acceleration.
The velocity arrow also answers the travel question: the object moves the way that arrow points.
To name the sense, carry the object a short way along its velocity arrow and read the drawing: clockwise or counterclockwise, as drawn on the page.
At the top of a circle, a tangent arrow pointing right carries the object from the 12 position toward the 3. The object is moving clockwise.
The acceleration arrow never answers the travel question. It aims at the center for either sense.
Henrik's diagram: the object at the top of the circle, one arrow pointing right on the tangent, one arrow pointing down at the center. Name the arrows and the direction of travel.
The rightward arrow lies on the tangent at the top: it is the velocity.
The downward arrow aims from the object at the center: it is the acceleration.
The object moves the way its velocity points: rightward at the 12 position, from the 12 toward the 3.
That way around is clockwise, as drawn on the page.
Velocity: the rightward arrow. Acceleration: the downward arrow. Travel: clockwise.
A second diagram: the object at the 9 o'clock position, one arrow pointing down on the tangent, one arrow pointing right at the center. Name the arrows and the direction of travel.
The downward arrow lies on the tangent at the 9 o'clock position: it is the velocity.
The rightward arrow aims from the object at the center: it is the acceleration.
The object moves downward at the 9 position, from the 9 toward the 6.
That way around is counterclockwise, as drawn on the page.
Velocity: the downward arrow. Acceleration: the rightward arrow. Travel: counterclockwise.
The diagram is drawn correctly. Which arrow is the cart's velocity?
The same diagram: the cart's velocity arrow points up at the 3 o'clock position. Viewed as drawn on the page, which way around is the cart traveling?
A new diagram, drawn correctly. Which arrow is the rider's acceleration?
The diagram is drawn correctly. Viewed as drawn on the page, which statement about it is true?
The diagram is drawn correctly. Which statement about it is true?
The diagram is drawn correctly. Which statement about it is true?