00:01
So we have this 220 new trunk resting on the floor.
00:09
And we know that the coefficient of static friction between the trunk and the floor is 0 .41.
00:16
The coefficient of kinetic friction is 0 .32.
00:21
And we know that the weight force of the trunk is 220 newtons, because that's how much it weighs.
00:28
This implies that this trunk has a mass.
00:34
Of weight divided by gravity.
00:38
And so that would be 220 newtons divided by 9 .8 meters per second squared.
00:46
And so it has a mass of roughly 22 .45 kilograms.
00:53
And in part a, we would like to calculate the minimum horizontal force with which a person must push on the trunk to start it moving.
01:02
And so in order to start the trunk moving, we need to push on the trunk with such a force that it is equal to the force of static friction.
01:13
So this implies that the force that they're pushing with is equal to force of static friction, and we know that force of static friction is equal to the coefficient of static friction times the normal force.
01:27
We know that the normal force is pointing upwards, and the weight force is down.
01:35
And we know that because there's no acceleration in the y direction, that normal force is equal to weight force.
01:42
And so that implies that normal force is equal to 220 newtons.
01:48
We can just plug in values here.
01:51
And we get 0 .41 times 220 newtons...