00:01
A force of 80 newtons is applied to a block of ice on a smooth, frictionless floor.
00:07
We're told that it starts from rest and is pushed a distance of 11 meters in a time of 5 seconds.
00:17
And we want to know, first of all, what is the mass of this block? and so we're going to first find acceleration.
00:24
And the reason for that is force is equal to mass times acceleration.
00:28
We don't have acceleration, but we have enough information.
00:30
Information to find it.
00:32
And so we're going to use the equation displacement is equal to initial velocity times time plus one -half acceleration times time squared.
00:41
Initial velocity is simply zero.
00:45
And so now we have this equation.
00:47
Multiply both sides by two in the attempt to get acceleration by itself and then divide by t squared or time squared.
00:55
And that gives us our equation for acceleration.
00:58
And so acceleration is equal to two times our distance divided by our time squared.
01:06
And when we do that, we get 0 .88 meters per second squared.
01:12
So now let's plug this into our equation.
01:14
So we have force is equal to mass times acceleration.
01:17
Let's go ahead and divide both sides by acceleration to get mass by itself.
01:22
And so mass is equal to force divided by acceleration.
01:28
And when we plug this in, we get a mass of 90 .9 kilograms to keep it in our three significant figures.
01:36
The next thing we want to know is if at this point the worker quits pushing, he just lets it go...