# Some doubts regarding rotational dynamics

• dreamz25
In summary, when a ball is tied to a string and rotated horizontally, the only external force acting on it is the tension from the string. This cancels out the force of gravity acting vertically downward. The net external force on a mass rotating in a circular path would depend on the direction of the rotation.
dreamz25
a) suppose we tie a ball with a string and rotate it keeping its other end tied with one of our fingers then the only external force acting on it is the tension. Which force then cancells 'mg' acting vertically downward?

b) if a mass is rotating in a circular path then in which direction does the net external force acting on it acts?

dreamz25 said:
a) suppose we tie a ball with a string and rotate it keeping its other end tied with one of our fingers then the only external force acting on it is the tension. Which force then cancells 'mg' acting vertically downward?
Not exactly sure what you are describing. But if you twirl the ball on the end of a string in a horizontal circle, the string will make an angle with the horizontal. The net vertical force will be zero.
b) if a mass is rotating in a circular path then in which direction does the net external force acting on it acts?
What do you think?

## 1. What is rotational dynamics?

Rotational dynamics is a branch of physics that deals with the motion of objects that rotate around an axis. It involves studying the forces, torques, and angular motion of these objects.

## 2. How is rotational motion different from linear motion?

Rotational motion involves objects spinning or rotating around an axis, while linear motion involves objects moving in a straight line. In rotational motion, the velocity and acceleration are measured in terms of angular velocity and angular acceleration, while in linear motion they are measured in terms of linear velocity and linear acceleration.

## 3. What is the relationship between torque and angular acceleration?

Torque is the measure of the rotational force applied to an object, while angular acceleration is the rate of change of an object's angular velocity. The relationship between torque and angular acceleration is given by the equation: torque = moment of inertia * angular acceleration.

## 4. How does the moment of inertia affect rotational motion?

The moment of inertia is a measure of an object's resistance to rotational motion. Objects with a larger moment of inertia will require more torque to achieve the same angular acceleration as an object with a smaller moment of inertia. This means that objects with a larger moment of inertia will rotate more slowly compared to objects with a smaller moment of inertia.

## 5. What are some real-life examples of rotational motion?

Some common examples of rotational motion include a spinning top, a spinning wheel, a merry-go-round, a rotating fan, and the Earth's rotation around its axis. Rotational motion is also important in many sports, such as figure skating, gymnastics, and diving, where athletes perform rotations around a fixed axis.

Replies
14
Views
630
Replies
32
Views
1K
Replies
9
Views
1K
Replies
3
Views
1K
Replies
24
Views
2K
Replies
2
Views
577
Replies
2
Views
1K
Replies
3
Views
2K
Replies
27
Views
2K
Replies
10
Views
2K