00:01
A person is pushing on a shopping cart with a mass of 16 kilograms.
00:06
We're told that it is moving at a constant velocity, so that automatically tells us our net force will be equal to zero.
00:12
So let's draw a free body diagram.
00:14
So here is the cart.
00:15
We have force of gravity going down.
00:18
This normal force is going up.
00:20
We're told that they are pushing at an angle of 29 degrees below the horizontal.
00:26
We don't know what this force is, but we do know that there is a frictional force.
00:31
Of 48 newtons.
00:33
So first thing we want to know is what is the force that the shopper exerts? and so since our net force is zero, we have our force of friction, which is going to be in the negative direction, plus the x component of this force right here.
00:54
So force in the x is going to be equal to zero.
00:58
So these two forces will be equal to each other.
01:00
So the force in the x is equal to force of friction when we bring it to the other side.
01:05
So force in the x, you can see we're going to make this a right triangle.
01:08
Force in the x is the adjacent part of that triangle, and when you're looking for the hypotenuse.
01:12
So we're going to have force, and the x is force times cosine of 29, because we want the x component.
01:22
And our force of friction is 48.
01:24
And so you're going to divide both sides by cosine of 29, this divided by cosine of 29.
01:33
And when you plug this into, a calculator, you get approximately 54 .9 newton...