Question

HELP!!
A 1.0 kg object is attached to a string 0.50 m. It is twirled in a horizontal circle above the ground at a speed of 5.0 m/s.
The direction of the velocity at the point shown points toward which letter?

Answer 1

Hint: What does Newtons first law predict?

Answer 2

an object in motion will stay in motion unless acted on by another opposite force?

Answer 3

The object is being twirled in a circle. So it is under the influence of centripetal force. In what direction does the centripetal force act?

Answer 4

it moves stuff towards the center of the circle

Answer 5

Yes, so the centripetal force is acting toward the center. This is true at any given point. Also at any point along the circular path, according to Newton's First Law, an object in motion wants to stay in motion (as you stated). So what direction would the object WANT to move in if there was no centripetal force? (Think about inertia/Newton's First Law.)

Answer 6

It would be D since the centripetal force would try to pull it towards the center, but if the centripetal force was not in action, then the object would rather go towards B. Is this logical? I think it makes sense..

Answer 7

Hmmm... not really? Newton's First Law states that an object in motion will stay in motion with a constant velocity (so same speed and same direction) as long as no outside force acts on it, due to its inertia. However, in this case, centripetal force IS acting on the object at all times. So centripetal force pulls toward D. But the object doesn't get pulled to point D; in fact, it continues to move in a circular path. So the object's inertia must be acting in some other direction to produce circular motion. What direction would this be?

Think of this: if the string were to break at any given point on the circular path, the tension force (and thus the centripetal force) would stop acting on the object. If this happened, the object would move in the direction that its velocity is in (due to inertia). So what direction would this be?

Answer 8

It would move in the direction of C.

Answer 9

I'm not that good at this part of physics

Answer 10

You're correct. It would move in the direction of C. The unit you're referring to is circular motion, correct? When in comes to objects in uniform circular motion, the centripetal force acts on the object in a direction toward the center. The velocity vector points tangent to the circular path, in the direction that the object is moving at that point. So the velocity vector and the vector of centripetal force are perpendicular to each other. What this means is that because the force acts in a direction perpendicular to the velocity, the object's direction changes, but its speed does not. So if the direction of the object is CONSTANTLY changing, while the speed stays the same, this would mean that the object is moving in a circle! So in this situation, the centripetal force is provided by the tension force of the string. The velocity vector indicates the direction that the object wants to go in (in the absence of centripetal force) due to its inertia. This velocity vector, because it is perpendicular to the centripetal force, is TANGENT to the circle. So, in the context of this problem, the centripetal force acts toward point D. Because the velocity vector is perpendicular to the centripetal force vector, it is tangent to the circle. This means that the velocity vector is pointing toward either point A or point C. However, the diagram indicates that the object is moving CLOCKWISE in a circular path. The velocity vector indicates the direction in which the object wants to move. So the velocity vector must point to point C. I hope this helps...? :)

Answer 11

OH! That makes sense! Thank you for all your help :) Your getting a medal.

Answer 12

No problem, glad to help.