Math Is Fun Forum

wayne

Member

Registered: 2007-08-16

Posts: 1

How much force will it take to make a 500 pounds barbell move?

1) How much force will it take to make a 500 pounds barbell move?

2) How much force then after it is "in motion" will it take to keep it moving at the same speed?

3) How much force will it take to then cause it to accelerate once in motion?

My answers, am I right or wrong?

1) If you load a barbell with 500 pounds and apply 500 pounds of force in an attempt to dead lift it, you will not move the 500 pounds, you need to apply 500.1 pounds to move the barbell.

2) But once it's moving at a constant speed, you need to apply 500 pounds of force only, and it will keep moving at this speed.

3) 500.2, 500.3 and 500.4 to keep it accelerating. If the force is reduced, the barbell will decelerate, if it is increased the car will accelerate, and if it matches, or equals the force, it will be in balance, or equal.

       
Jay

Last edited by wayne (2007-08-16 12:53:23)

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: How much force will it take to make a 500 pounds barbell move?

If depends what you mean by "move".

Your answers are right if the question is talking about lifting the barbell, but if you just want to drag it along the floor then the numbers will be less.

This time, you're interested in how much friction there is between the barbell and the floor. This can be given a number between 0 and 1 depending on how much there is. This number is generally called μ.

Once you know μ, you just multiply all your previous answers by that to get the new answers.
So for a very sticky floor, the numbers will be close to the ones you had already, but on ice they'll be much closer to 0.

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Why did the vector cross the road?
It wanted to be normal.