Cracking Nuts with Pliers: Estimating Hand Force Needed

In summary, the problem involves determining the force required for a person's hand to crack a nut using a pair of pliers. The figure shows a scale drawing of the pliers and the force required is given to be 300 N. To solve this problem, the concept of mechanical advantage is used, which is the ratio of the input force (force applied by the hand) to the output force (force applied to the nut). By looking at the moment (or torque) applied vs. output, it is determined that the magnitude of the torque at one end must be the same as that at the other end. Using basic geometry and measurements, the resulting force is calculated to be 90 N.
  • #1
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Homework Statement


The figure shows scale drawing of a pair of pliers being
used to crack a nut, with an appropriately reduced centimeter grid.
Warning: do not attempt this at home; it is bad manners. If the
force required to crack the nut is 300 N, estimate the force required
of the person's hand.( The Handle is 10cm)


Homework Equations


MA=input force/output force


The Attempt at a Solution


Is this even possible to get the Input force without knowing the MA?
 
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  • #2
You need the mechanical advantage - but this is just the ratio of the handle length to the jaw length (a nutcracker is just a see-saw)
 
  • #3
You don't need mass or acceleration in this case - you are already given the force. For this problem, you need to look at the moment (or torque) applied vs. output.
 
  • #4
I think the OP is using MA to mean mechanical advantage (actually strictly speaking in this case - it's velocity ratio)
 
  • #5
Mechanical Advantage is what i need. So this problem doesn't have enough information?
 
  • #6
The pliers are not moving, so their angular momentum remains constant
at zero, and the total torque on them must be zero. Not only that, but each half of the pliers
must have zero total torque on it. This tells us that the magnitude of the torque at one end
must be the same as that at the other end. The distance from the axis to the nut is about 2.5

cm, and the distance from the axis to the centers of the palm and ngers are about 8 cm. The
angles are close enough to 90  that we can pretend they're 90 degrees, considering the rough
nature of the other assumptions and measurements. The result is (300 N)(2.5 cm) = (F)(8 cm),
or F = 90 N.
183 I found this at the back of the book.I stil don't get it 8*90 =720 and 300*2.5=750
 
  • #7
You haven't included the drawing - but presumably you can estimate the distances pivot-nut and pivot-hand, the ratio of these is the mechanical advantage (assuming 100% efficency)
 

Related to Cracking Nuts with Pliers: Estimating Hand Force Needed

1. How do you estimate the hand force needed to crack nuts with pliers?

The hand force needed to crack nuts with pliers can be estimated by considering the type of nut being cracked, the size and shape of the nut, and the type of pliers being used. It is also important to take into account the strength and grip of the person using the pliers.

2. What factors affect the hand force needed to crack nuts with pliers?

The type of nut, size and shape of the nut, type of pliers, and the strength and grip of the person using the pliers are all factors that can affect the hand force needed to crack nuts with pliers. Other factors may include the age and condition of the pliers, as well as the technique used by the person cracking the nuts.

3. Is there a specific technique to cracking nuts with pliers?

While there is no one specific technique, some common tips for cracking nuts with pliers include gripping the nut firmly between the jaws of the pliers, positioning the nut in the center of the jaws, and applying steady pressure with the hand while gently twisting the pliers back and forth.

4. Are there any safety precautions to keep in mind when cracking nuts with pliers?

Yes, it is important to be mindful of your hand placement and grip on the pliers to avoid injury. It is also recommended to wear protective gloves to prevent any potential cuts or bruises. Additionally, make sure to use pliers with a comfortable grip and check for any defects or damage before use.

5. Can pliers be used to crack all types of nuts?

Pliers can be used to crack most types of nuts, but it is important to choose the right type of pliers for the job. For example, slip-joint pliers may work well for smaller nuts, while locking pliers or groove joint pliers may be better suited for larger or harder nuts. It is always best to test the pliers on a few nuts before attempting to crack a large batch.

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