: Why do we have more force with an object when it’s longer (for example bending metal with a long metal stick that is a few meters away)
In: 4
The term and effect is called “leverage”. And it exists because of the fact that the amount of work you do to move something is equal to the force you used × distance you moved. If you want to increase the amount of work you do, you can either increase your force (push harder) or increase the distance you move (use the long handle).
If you imagine a bar connected to a shaft that can rotate.
O———–
Like that (imagine it viewed from above).
The further out you are from the shaft when you push on that bar, the further you have to walk to make the shaft turn the same amount, say one full rotation. That’s more work you’re putting in to turn the shaft by the same amount. That means the rotational force (torque) with which that shaft is turning is increased.
All this assumes you’re putting the same force onto the bar and walking at the same speed both times.
This is why torque is described in inch-pounds, or foot-pounds, or newton-metres. It’s literally how far out on the imaginary bar you are, and how hard you’re pushing.
That principle works for levers too.
What you’re talking about is a lever. One of the basic machines. The simple principle behind it is by increasing the distance you move to exert the same amount of force you make it easier. So for example if you need to exert 200 lbs of force over two inches that means you have to exert 100 lb / in. adding a lever increases the distance you have to travel, making the force smaller. So now you have, say, 20 inches to exert that 200 lbs of force, now instead of 100 lb/in, it’s only 10 lb/in.
You’ve constructed a lever. Twisting or rotational force is known as torque; it is calculated by multiplying the linear force being exerted by the distance between where the force is being exerted and where the rod/beam/shaft can pivot, also known as the fulcrum. So if you were pushing down with 100 Newtons of force on a 1.5 meter long crank handle, you would be applying 150 N-m of torque to the crank.
If we’re talking twisting or bending metal, that means you can apply a lot more force by simply being farther away and moving more. If you bend a 2 meter long rod by 90 degrees, you have to move about 3.14 meters to bend the rod at the fulcrum (2 pi r / 4). You are trading distance for force; it would be very difficult to bend the rod in your hands, but you’d only have to move your hands a few centimeters to bend it.
It’s because you’re no longer trying to push it, you’re trying to twist it. This means that you’re using torque, not a force. Torque is the force multiplied by the distance so it inherently changes as you move closer or further.
A good thing to keep in mind is that rotating things behaves differently than pushing them. You’ll run into stuff like this a lot.
The way I learnt it is think angles for something like hockey
As a goalie if there is a person 1 foot in front of you with the puck and he moves 1 foot to your right, you have to move 1 foot to the right to cover the net (not exact measurements but close enough) if he is at the blue line and moves 1 foot to the right you have to move like 2 inches to the right to still be in line, you’re moving farther to get the same amount of movement out of the goalie
The term that you are describing is a moment. It equals force times distance. The further the distance where force is applied, the larger the moment.
It takes the same ‘effort’ (work, energy) to move a thing a certain distance. You can do something easy over a long distance or something hard over a short distance.
Think of bike gears. At a low gear it’s really easy to pedal but you have to pedal really fast to actually move. At a high gear you don’t have to pedal as much to go fast, but it’s hard to pedal.
Give me a lever long enough and a fulcrum on which to place it, and I shall move the world
-Archimedes
Latest Answers