What causes the sideways motion in circular motion?

In summary, the ball on a string goes left and right because the initial speed causes it to do so. The only work done is by gravity, which is always towards the center of the Earth.
  • #1
DavidWi
10
0
Ok, right now in my college physics class, we're going over work in a circular motion. I see how gravity does the amount of work that the thing falls in a circular motion. However, my teacher told us that the tension of the string does no work. Gravity makes the ball go down, so gravity does taht work. What causes the work that makes the ball go to the side. the only work I can see in this example is gravity working down, but if that were true, then we wouldn't have the ball going left and right. Could anyone help me and tell me how the ball on the string can go left and right if the only work on it is gravity?
 
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  • #2
Work is only done when an object moves in the direction of the Force. In other words, if the string length remains constant (and taut) it can't do any work.
 
  • #3
The ball goes left and right due to the initial speed. Gravity keeps it in a circular orbit.
Suppose we have a spaceship. When the spaceship takes off, the rockets do work and push it into orbit, giving it an initial speed. Then, suppose that the spaceship throws out a satellite. The satellite just moves in uniform circular motion. Since gravity is always towards the centre of the Earth, and the spaceship always moves along it's circular orbit, gravity does no work.

Your teacher is referring to the part where the object experiences uniform circular motion and is no longer accelerating.
 
  • #4
DavidWi said:
Ok, right now in my college physics class, we're going over work in a circular motion. I see how gravity does the amount of work that the thing falls in a circular motion. However, my teacher told us that the tension of the string does no work. Gravity makes the ball go down, so gravity does taht work. What causes the work that makes the ball go to the side. the only work I can see in this example is gravity working down, but if that were true, then we wouldn't have the ball going left and right. Could anyone help me and tell me how the ball on the string can go left and right if the only work on it is gravity?

I assume you are holding the string in your hand and swinging the ball over your head so that the ball is traveling on the horizontal axis to normal human veiw and is making a circular path perpendicular to the center of the earth.

According to the physics book I'm reading, gravity isn't exerted horizontally upon the ball. It may only exert a force upon the ball vertically.

When ball is not in circular motion, it will hang on the end of the string according to the first law, at rest. To get the ball into circular motion, you must do work upon it. At a constant rotation speed in air there is friction. The ball will try to slow, so a constant force is necessary to keep it's circular speed constant, which means work is being applied to the ball being swung in air.

The force doesn't skip the string, going from the your hand strangely to the ball. Force is exerted through the string, therefore work is done on the ball.

But, I'm not to the tension chapter of physics. So, I don't know what is meant by tension. Maybe the 'tension' of the string does not do work. If it doesn't, then 'what' of the string does do work is what I would ask my instructor.

I'd be carefull to, sometime my book says to ignore other forces to isolate a specific thing. This explanation would change if air resistance is taken out of the picture.
 
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FAQ: What causes the sideways motion in circular motion?

What is work in a circular motion?

Work in a circular motion refers to the application of force on an object that moves in a circular path. This type of work involves a force acting on an object at a distance from its center of rotation, causing the object to move in a circular motion.

What are some examples of work in a circular motion?

Examples of work in a circular motion include a car turning a corner, a spinning top, or a planet orbiting around the sun. In each of these cases, a force is applied to the object in a direction perpendicular to its motion, causing it to move in a circular path.

What is the relationship between work and circular motion?

The relationship between work and circular motion is that work is the product of force and displacement. In circular motion, the force is acting perpendicular to the displacement, resulting in work being done on the object. The work done can be calculated using the formula W = Fd, where W is work, F is force, and d is displacement.

How is work in a circular motion different from work in a straight line?

Work in a circular motion is different from work in a straight line because the force and displacement are not in the same direction. In a straight line, the force and displacement are parallel, resulting in work being done in the same direction. In circular motion, the force is acting at an angle to the displacement, resulting in work being done perpendicular to the direction of motion.

What are the applications of work in a circular motion in real life?

Work in a circular motion has many applications in real life, such as in the operation of machinery and vehicles. For example, the circular motion of gears in a car's transmission allows for the transfer of power from the engine to the wheels. It is also used in the design of roller coasters, where the circular motion of the tracks allows for the safe and thrilling movement of the carts. Additionally, the rotation of objects, such as wheels and pulleys, is essential in many mechanical systems.

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