Requesting help with centripetal acceleration homework

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SUMMARY

The discussion centers on calculating the speed required for a hockey puck, with a mass of 0.08 kg, to maintain circular motion on a smooth tabletop while a 1.00 kg mass hangs vertically. The relevant equations include F=ma and Ac = (v^2/r). Participants clarified that gravitational forces on the puck do not affect the tension in the string due to the absence of friction on the smooth surface. The normal force from the table counteracts the puck's weight, confirming that gravity does not influence the puck's horizontal motion.

PREREQUISITES
  • Understanding of centripetal acceleration (Ac = (v^2/r))
  • Knowledge of Newton's second law (F=ma)
  • Familiarity with forces acting on objects in circular motion
  • Basic concepts of tension in strings and normal forces
NEXT STEPS
  • Study the relationship between tension and centripetal force in circular motion
  • Learn about the effects of friction on motion in physics
  • Explore the concept of normal force and its role in equilibrium
  • Investigate real-world applications of centripetal acceleration in sports
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Students studying physics, particularly those focusing on mechanics and circular motion, as well as educators seeking to clarify concepts related to forces and motion.

Myani
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Homework Statement


A hockey puck of mass m = 80 g is attached to a string that passes through a hole in the center of a table, as shown in the figure below. The hockey puck moves in a circle of radius r = 1.10 m. Tied to the other end of the string, and hanging vertically beneath the table, is a mass M = 1.00 kg. Assuming the tabletop is perfectly smooth, what speed must the hockey puck have if the mass M is to remain at rest?

M puck = 0.08kg
M block = 1kg
Gravity = 9.8
r = 1.10

Homework Equations



F=ma
Ac = (v^2/r)

The Attempt at a Solution



Attached in photo, why the gravity force of puck not being included is confusing me a lot, shouldn't all objects be affected by gravity?
 

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Myani said:
Attached in photo, why the gravity force of puck not being included is confusing me a lot, shouldn't all objects be affected by gravity?
Do you feel gravitational force on the buck has any influence on the tension of the string? Are they not acting perpendicular to each other over the buck? Moreover, the table surface is smooth, right?
 
You'll need someone else to verify if this is correct or not as my physics know-how is a bit dated these days. However, I believe gravity comes into play in the form of friction against the surface. Since we're assuming the tabletop is perfectly smooth, gravity on the puck is no longer a factor because there is no friction. Gravity's pull in this case is counteracted by the table.
 
Myani said:

Homework Statement


A hockey puck of mass m = 80 g is attached to a string that passes through a hole in the center of a table, as shown in the figure below. The hockey puck moves in a circle of radius r = 1.10 m. Tied to the other end of the string, and hanging vertically beneath the table, is a mass M = 1.00 kg. Assuming the tabletop is perfectly smooth, what speed must the hockey puck have if the mass M is to remain at rest?

M puck = 0.08kg
M block = 1kg
Gravity = 9.8
********** 9.8 what? **************
r = 1.10
********* 1.10 what ****************

Homework Equations



F=ma
Ac = (v^2/r)

The Attempt at a Solution



Attached in photo, why the gravity force of puck not being included is confusing me a lot, shouldn't all objects be affected by gravity?

Units are important; do not state units for two of the data items and omit them for two others.
 
Myani said:
why the gravity force of puck not being included
Because the normal force from the table is equal and opposite to it, so they cancel. And as others have mentioned, there is no friction.
 
Thank you for all your responses, I am able to understand it now.

Also next time I will make sure to add all the units to my variables.
 

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