Rotational kinematics/dynamics

  • Thread starter EndoBendo
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In summary, a juggler is able to handle four balls simultaneously, taking 0.5 seconds to cycle each ball through his hands, throw it, and be ready to catch the next ball. To juggle five balls, he would need to throw each ball with enough velocity to stay in the air for 3.5 seconds and reach a high enough height. This would require an understanding of rotational kinematics equations and rotational kinetic energy.
  • #1
EndoBendo
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Homework Statement



A juggler is able to handle four balls simultaneously. He takes 0.5 s to cycle each
ball through his hands, throw the ball, and be ready to catch the next ball. (a)
With what velocity must he throw each ball up? (b) What is the position of the
other three balls when he has just caught one of the balls? (c) How high must he
throw the balls if he is to juggle five balls?

Homework Equations



Rotational kinematics eqns.
Rotational kinetic energy
etc.

The Attempt at a Solution



I'm not really sure.. A point in the right direction would help..
 
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  • #2
EndoBendo said:

Homework Statement



A juggler is able to handle four balls simultaneously. He takes 0.5 s to cycle each
ball through his hands, throw the ball, and be ready to catch the next ball. (a)
With what velocity must he throw each ball up? (b) What is the position of the
other three balls when he has just caught one of the balls? (c) How high must he
throw the balls if he is to juggle five balls?

Homework Equations



Rotational kinematics eqns.
Rotational kinetic energy
etc.

The Attempt at a Solution



I'm not really sure.. A point in the right direction would help..

If he has just caught ball 1, he will throw that ball up in 0.5 seconds time.
At that same time [probably a fraction later] he will catch Ball 2

t= 0 catch ball 1
t = 0.5 throw ball 1 & catch Ball 2
t = 1.0 throw ball 2 & catch ball 3
t = 1.5 throw ball 3 & catch ball 4
t = 2.0 throw ball 4 & catch ball 1 again
etc.

So 1.5 seconds after throwing ball 1, he catches it again.

How fast does he have to throw it if it doesn't come back for 1.5 seconds?
How high will it get in that time?

Perhaps the idea of throwing one ball and catching the next at the same time if too far fetched.
Perhaps it is
t = 0 catch ball1
t = 0.5 throw ball 1
t = 1.0 catch ball 2
t = 1.5 throw ball 2 etc
.
.
.
t = 4.0 catch ball 1 again, so the ball has to be in the air for 3.5 seconds? For that to happen it would have to be one hell of a throw!
 

Related to Rotational kinematics/dynamics

1. What is rotational kinematics?

Rotational kinematics is the study of the motion of objects that rotate about a fixed axis. It involves measuring quantities such as angular displacement, velocity, and acceleration.

2. How is rotational kinematics different from linear kinematics?

Rotational kinematics deals with the motion of objects that rotate, while linear kinematics deals with the motion of objects that move in a straight line. Some key differences include the use of angular measurements (such as radians) instead of linear measurements (such as meters) and the presence of torque, which is a rotational equivalent of force.

3. What is the equation for angular velocity?

The equation for angular velocity is ω = Δθ/Δt, where ω is the angular velocity in radians per second, Δθ is the change in angular displacement, and Δt is the change in time. This equation is similar to the linear velocity equation, v = Δx/Δt, but uses angular displacement instead of linear displacement.

4. What is rotational inertia?

Rotational inertia, also known as moment of inertia, is a measure of an object's resistance to changes in its rotational motion. It depends on the mass of the object and its distribution of mass relative to the axis of rotation. Objects with a larger rotational inertia will require more torque to produce a given angular acceleration.

5. How is rotational dynamics related to rotational kinematics?

Rotational dynamics is the study of the causes of rotational motion, while rotational kinematics is the study of the resulting motion. In other words, rotational dynamics explains why objects rotate and how forces and torques affect their rotation, while rotational kinematics describes the resulting motion in terms of angular displacement, velocity, and acceleration.

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