cation Friction and Inclines Pushing a Block 1 of 13 Part A Learning Goal: To un

Question

cation Friction and Inclines Pushing a Block 1 of 13 Part A Learning Goal: To understand kinetic and static trickon If the block is at rest (and the orly foroes acting on the block are the force due to gravity and the normail orce from the table), what is the magnitude of the force due to ficion? A block of mass m les on a honizontal tabie. The coeficient of static fricticn bebeeen the block and he table is I The coficient of kinetic friction is View Available Hinijs) Part B Suppose you wanl to move the block, but you want to push it with the loast ce possbto get mong wth what force Frust you be pushing trie block ?st belore the wok begesto"ove? Express the magnitude of in terms of some or all the variables and , as well Vw Avalable His MacBook Air

Explanation / Answer

Part A:

It is given that the forces acting onto the block is are only gravittional force and therfore it is static means lying onto the table. Hence the block is not in motion and therfore the friction applied in this case would be static.

So, the static friction would be :

Fs = us*N => us*m*g

where us = static friction coefficient

N = normal reaction

m = mass of the block.

g = gravitational constant.

Part B:

To move the block one must apply the force that should be greater than the static friction force.
Hence, F >= Fs

F >= us*N

F >= us*m*g

This would be the minimum force required to displace the block from its static postion.

Part C:

When the force applied is half of that needed,

F = Fs/2 the block won't move.

And therfore, the friction force would still be static that is Fs.

Hence friction force acting upon block would be:

Fs = us*m*g.

Part D:

Let F be the continued force applied.

Then when it just starts moving that means the enough force applied would have might been greater than the static friction force and therfore, F = Fs and after continued force applied the force act would be kinetic.
Hence, the net force would be:

F - Fs = ma

a = (F- Fs)/m => (us - uk)g m/s2

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