Finding the Force Applied to a Heavy Bag

In summary, the problem involves determining the amount of force required to move a cylindrical bag with a radius of 0.15m and a height of 1m, weighing 36 kg and hanging 0.4m away from a point by a chain. The speed/acceleration of the bag is not necessary to consider since the bag will continue to move farther with more force applied. The elasticity of the bag's surface is also unknown. Additional information needed includes whether the bag pivots or swings from the ceiling. The energy of the kick goes into lifting the center of mass of the bag against gravity, and the energy can be calculated by considering the distance the bag moves and the angle of the swing. To account for losses, the
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I have a heavy bag and I was wondering if I could find out how much force is applied when I kick it. Here's a picture describing of the problem:

5061011c70cd9.jpg


If some amount of force is applied that causes the bag to move x meters (first swing) in the direction of the force, how much was applied? The bag is cylindrical, with a radius of 0.15m and a height of 1m. It has a mass of 36 kg and is hanging 0.4m away from a point by chain.

I don't think the speed/acceleration of the bag is necessary because requiring either of those things suggest that there's more than one value for force that would cause the bag to move a certain amount. Wouldn't the bag just move farther and farther as more force was applied?

Something that I think is important that I currently do not know is how elastic (is that what it's called?) the surface of the bag is (that is, how much the bag "caves in" on itself when hit), so just assume something reasonable.

Thanks! If there's any information you need about the situation then ask and I'll supply everything I can.
 
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  • #2
Does the bag really pivot as shown or does it swing from the ceiling?

Note: the energy of your kick (+losses) goes into lifting the center of mass of the bag against gravity. If I take the pivot at the ceiling, the com of the bag is 0.9m down. If the bottom of the bag moves x meters, then the com moves a similar distance by similar triangles. You can also find the angle of the swing since ##1.4\sin(\theta)=x## and so ##0.9-0.9\cos(\theta)=y## and so the energy in your kick is more than ##K=mgy##.

You can work out the extra by displacing the bag by distance x, and seeing how far over the other side it goes. If it is very close to x, then there is not much loss.

For more accurate modelling, you can set it swinging and work out the damped harmonic motion.
 

1. What is the formula for finding the force applied to a heavy bag?

The formula for finding the force applied to a heavy bag is: F = m x a, where F is the force in Newtons, m is the mass of the bag in kilograms, and a is the acceleration in meters per second squared.

2. How do I measure the mass of the heavy bag?

The mass of the heavy bag can be measured using a scale. Place the bag on the scale and record the measurement in kilograms.

3. How do I measure the acceleration of the heavy bag?

The acceleration of the heavy bag can be measured using a motion sensor or a smartphone app. Attach the sensor or open the app and record the acceleration in meters per second squared.

4. Can I use the same formula to find the force applied to any object?

Yes, the formula F = m x a can be used to find the force applied to any object as long as the mass and acceleration are known.

5. How accurate is this method for finding the force applied to a heavy bag?

This method is fairly accurate as long as the measurements for mass and acceleration are precise. Factors such as air resistance may slightly affect the accuracy, but it is still a reliable way to estimate the force applied to a heavy bag.

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