Acceleration & velocity using instantaneous centre of zero velocity

In summary, the conversation discusses a link that is connected by two bearings A and B, which run along slots at right angles to each other. The length of the link AB is 0.2m, and at a specific instant, the height H is 0.05m and bearing A has a constant velocity V of 0.1m/s upwards. The conversation then moves on to calculating the velocity of bearing B, the angular velocity of link AB, the acceleration of bearing B, and the angular acceleration of link AB. Different approaches and equations are suggested, but it is unclear how they relate to the problem at hand. Ultimately, the desired quantities are not calculated and the conversation remains unresolved.
  • #1
Ctom101
3
0
1. A link is connected by two bearings A and B. The bearings run along slots which are at right angles to each other. The length of the link AB (length between the centres of bearings A and B) is 0.2m. At an instant of time, height H, is 0.05m, and the bearing A has a constant velocity V, of 0.1m/s upwards.
At the instant of time calculate;
The velocity of bearing B.
The angular velocity of the link AB.
The acceleration of bearing B.
The angular acceleration of the link AB


2. velocity B = distance from rotational centre x angular velocity of link AB.
angular velocity of link AB = velocity A / distance from centre of zero velocity

3. from the working out in my picture changing it into a triangle I think I have worked out the velocity of bearing B and the angular velocity of link AB, but I don't know how to find the acceleration of B or the angular acceleration of AB.
Could somebody please help me with this and let me know if what I've done so far is incorrect?

The Attempt at a Solution


a = 0.05 c = 0.2
a2 + b2 = c2
0.22 / 0.052 = 16 root 16 = 4 b = 4
velocity A / distance from centre of zero velocity
0.1 / 0.05 = 2rad/s angular velocity of link AB
velocity B = distance from rotational centre(b) x angular velocity link AB
4 x 2 = 8m/s

ωv AB = 2rad/s
v B = 8m/s
 

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  • #2
You have to exploit the relationship between A and B ... i.e. the dimensions of the triangle.
I don't understand your working though.

If I put c=|AB|, with the position of B as x and the position of A as y, then

c^2=x^2+y^2

...differentiate through by time to get the relationship between the velocities, and again to get the accelerations.
what is the acceleration of A?
 
  • #3
It says A has a constant velocity of 0.1m/s, so I think acceleration is 0

Looking over it again I think I worked out the length b incorrectly.

link AB = 0.2m
Height = 0.05m

Pythagoras: a^2 + b^2 = c^2

link AB = c
Height = a

c^2 - a^2 = b^2

0.2^2 - 0.05^ = 0.0375
root 0.0375 = 0.1936
b = 0.19
 
  • #4
angular velocity of link AB = velocity A / distance from centre of zero velocity

velocity A = 0.1m/s
distance from centre of zero velocity (a) = 0.05m
0.1/0.05= 2rad/s

velocity B = distance from centre of zero velocity x angular velocity of link AB

angular velocity of AB = 2rad/s
distance from centre of zero velocity (b) = 0.19

0.19 x 2 = 0.38m/s
velocity B = 0.38m/s

I think this is now right but I don't know how to move on for;
The acceleration of bearing B.
The angular acceleration of the link AB
 
  • #5
I still don't see how your reasoning arrives at the required quantities.

What does "center of zero velocity" mean?
You seem to be giving the velocity of A in radiens per second as if it were moving perpendicular to the corner.
Is this correct?

What's wrong with the suggestions I already gave you?
 

FAQ: Acceleration & velocity using instantaneous centre of zero velocity

1. What is acceleration using instantaneous centre of zero velocity?

Acceleration using instantaneous centre of zero velocity is a method of calculating the acceleration of an object at a specific point in time. It takes into account the object's velocity and position at that moment, as well as the radius of curvature of its path.

2. How is instantaneous centre of zero velocity used to calculate acceleration?

The instantaneous centre of zero velocity is the point on an object's path where its velocity is momentarily zero. By considering this point and the object's position and velocity, we can use the formula a = v^2/r to calculate its acceleration at that moment.

3. What is the difference between acceleration and velocity using instantaneous centre of zero velocity?

Acceleration using instantaneous centre of zero velocity is a method of calculating the acceleration of an object at a specific moment in time, taking into account its velocity and position. On the other hand, velocity using instantaneous centre of zero velocity is a method of calculating the velocity of an object at that same moment in time.

4. When is it useful to use the instantaneous centre of zero velocity method?

The instantaneous centre of zero velocity method is useful when dealing with objects that are accelerating in a curved path. It allows us to calculate the acceleration at a specific point in time, rather than an average acceleration over a period of time.

5. What are some real-world examples of using the instantaneous centre of zero velocity method?

This method is commonly used in fields such as physics and engineering, where objects often move in curved paths. For example, it can be used to calculate the acceleration of a car going around a curve or the acceleration of a rollercoaster on a loop. It is also used in sports, such as calculating the acceleration of a baseball as it curves through the air.

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