Rotational Motion change angular rotational

In summary, the correct answer for a force that can change angular rotation is a lever arm tangential to the direction of rotation. This is because applying a force through the axis of rotation or a moment arm parallel to the axis of rotation would result in a torque of 0, while applying it tangentially would result in a non-zero torque value. Additionally, the angle between the force and lever arm in this scenario would be 90 degrees, resulting in a maximum torque value.
  • #1
physgrl
138
0

Homework Statement



9. A force can change angular rotational if it acts through:

a. the axis of rotation

*b. a lever arm tangential to the direction of rotation

c. a moment arm parallel to the axis of rotation

d. none of these

Homework Equations



n/a

The Attempt at a Solution



I would like to understand why b is the correct answer.
 
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  • #2
I guess we could start with why it isn't a or c. Angular momentum is changed when Torque is applied. If you apply a force through the axis of rotation, then r is 0. if you apply force through a moment arm parallel to the axis of rotation then torque is also zero since

τ = F x r
|τ| = Frsinσ

since F and r are parallel, the angle is 0, therefore the torque is 0. If you applied it tangentially, then the σ value will be 90 and sinσ will be 1.
 
  • #3
Got it...thanks!
 
  • #4
physgrl said:
Got it...thanks!

Awesome. youre welcome :smile:
 
  • #5


The correct answer is b because in order for a force to change angular rotational motion, it must create a torque. Torque is defined as the product of force and lever arm (or moment arm) with respect to the axis of rotation. So, if the force is acting through the axis of rotation (option a), there will be no lever arm and therefore no torque. Similarly, if the force is acting parallel to the axis of rotation (option c), there will be no lever arm and no torque. However, if the force is acting tangential to the direction of rotation (option b), it will create a lever arm and therefore a torque, which can change the angular rotational motion. Therefore, option b is the correct answer.
 

1. What is rotational motion?

Rotational motion is the movement of an object around a fixed point or axis. It is also known as circular motion.

2. How does rotational motion differ from linear motion?

Rotational motion involves movement around an axis, while linear motion involves movement in a straight line. In rotational motion, the distance from the axis and the angle of rotation are important, whereas in linear motion, only the distance traveled is relevant.

3. What causes rotational motion to change?

Rotational motion can change due to two main factors: torque and angular momentum. Torque is the force that causes an object to rotate, and angular momentum is the measure of an object's tendency to continue rotating.

4. How does rotational motion affect everyday life?

Rotational motion is present in many everyday activities, such as driving a car, swinging a bat, or riding a bike. It is also essential in the functioning of many machines, such as fans, turbines, and gears.

5. What is the difference between angular rotational velocity and angular rotational acceleration?

Angular rotational velocity is the rate of change of angular displacement, while angular rotational acceleration is the rate of change of angular velocity. In simpler terms, angular rotational velocity measures how fast an object is rotating, while angular rotational acceleration measures how quickly the rotation is changing.

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