Is the Net Force at the Bottom of a Vertical Circle Greater or Lower Than MG?

AI Thread Summary
In the discussion about the net force at the bottom of a vertical circle, it is clarified that the net force is directed upward and is indeed greater than the gravitational force (mg). The confusion arises from the distinction between tension and net force; while tension at the bottom must exceed mg to provide the necessary centripetal force, the net force is the result of the tension minus the gravitational force. At the bottom of the circle, the upward tension adds to the downward gravitational force, leading to a net force that is greater than mg. Understanding this difference is crucial for grasping the dynamics of circular motion. The key takeaway is that as long as tension exceeds mg, there will be a net centripetal force present.
HelloMotto
Messages
73
Reaction score
0
You are whirling a rubber stopper of mass something attached to a string in a vertical circle at high constant speed. At the bottom of the circle, the net force that causes acceleration is

my answer was Vertically upward and greater in magnitude than MG.
but the answer in the book says
vertically upward and lower in magnitude than mg.

WHY? I don't get this.
At the bottom of the circle, The Centripetal force is the difference of Force tension pointing upwards and force of gravity pointing downwards. So if the netforce is smaller than MG, then there can't be a centripetal force...

please help me out.
 
Physics news on Phys.org
If I'm understanding you correctly, you are talking about the tension of bottom vs. top?

The top has less magnitude because the tension [up] is reduced by the Fg [down]. At the bottom, the magnitude is greater because it's tension [down] PLUS Fg [down].
 
You are thinking about the tension while they are asking about net force. As long as the tension is greater than MG, there will be some net centripetal force.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Thread 'Egg Drop Challenge! Need ideas for winning designs'

I was thinking using 2 purple mattress samples, and taping them together, I do want other ideas though, the main guidelines are; Must have a volume LESS than 1600 cubic centimeters, and CAN'T exceed 25 cm in ANY direction. Must be LESS than 1 kg. NO parachutes. NO glue or Tape can touch the egg. MUST be able to take egg out in less than 1 minute. Grade A large eggs will be used.
View full post »

Similar threads

Centripetal force - Ferris wheel... Opposite results
Replies
8
Views
1K
Vertical circle in a pendulum ride -- tension force acting on the gondola
Replies
7
Views
2K
Uniform Circular Motion: Tension Force at Top of Circle
Replies
4
Views
1K
Centripetal motion, the tension at the bottom of a circle
Replies
7
Views
4K
Three conceptual questions on centripetal acceleration in a cone
Replies
5
Views
2K
What actually is the centripetal acceleration formula?
Replies
28
Views
3K
Centripetal force throughout a vertical circle
Replies
9
Views
4K
Acceleration and Gravity with Circular Motion
Replies
9
Views
3K
Centripetal Lab- finding the mass from the slope
Replies
1
Views
3K
Differential Equation for a Pendulum
Replies
21
Views
2K

Hot Threads

Recent Insights

Back
Top