March-11-2015 Lab 6:Static Friction and Kinetic Friction

LAB 6 :Static Friction and Kinetic Friction

Purpose: the purpose of this lab is to using the equipment and find out the 

Static Friction and Kinetic Friction by changing the mass and pulling force.

For this lab, we have 5 different experiments.

Beginning

1).We need some different mass of blocks which have enough friction on it.

2). Cup with water, board, laptop, motion detector, and weight measurment.

1.Static fricition

  definition: Static friction describes the friction force acting between two bodies when they are not moving relative to one another.

For this experiment we need set up like this

We are going o add a litter bit of water each time to the cup until the block just start to slip, record the weight of the water.

And then put another block on that red block, and record the weight of water, 

and do it again. record weight of water when has three blocks.

This are the cup weights

and three blocks'mass and we will be using those block for the next five experiments

Here the record when it has red block, water weight 49.9g

when it has red block and normal block, water weight 119.5g

when it has red block, normal block, and blue block, the water weight 127.1g

Because we know that for the max static friction, it's mean that the block just slip, so friction

f = mg and plot the data; we get u = m/ M

u = 0.2985 for the max static friction. This is the static friction between red block and table.

2. Kinetic friction

Kinetic friction as be proportional to the normal force.

f(Kinetic friction) = u_k N  u_k = f(Kinetic friction)/N

For Kinetic friction is fixed not like the static force that will in between zero to max.

So set up the equipment like this.

Pulling the block with the force sensor, then the laptop will have the force vs time graph.

Then those are the force we pulling.
F1 = 0.4475N F2 = 1.24N F3 = 1.379 N

Then we plot the data with force vs N we got
u_ k = 0.2758

3. Static friction from a sloped surface.

Place a block on a horizontal surface. 

Slowly raise one end of the surface

until the block just starts to move

Record the angle.

We got when has red block angle is 15 degree.

We got when has red block and normal block, angle is 12 degree.

We got when has red block , blue block and normal block, angle is 10 degree.

Then after we did the calculation we got u_s = 0.34432

4. Kinetic friction from sliding a block down and incline

With motion detection in the top of an 

steep enough that a block will accelerate

down the incline, measure the angle of the incline and the acceleration.

and then determine the coefficient of kinetic friction between the block and surface 

We measure the angle is 30 degree.

We chose the part when acceleration is constant. we got a = 1.61 m/s^2 .

5. Predicting the acceleration of A two mass system,

The set up will be looking like this kind of picture.

with the motion detector on the other side

First we start with our experiment, and

The hanging mass weight is 50 g.

After we do the experiment on the laptop
we got

a = 0.2983 m ^2

And then we use our result from experiment 4 above.
See what we got the acceleration, and compare to this one.

after we plug all the data acceleration a = 0.362 m/s^2

one is a = 0.2983 another is 0.362, so our experiment is fine.

Conclusion

For this experiment, we have 5 parts in which will test different things and then use all the experiment to check our results.