Force of Friction - Lab report PDF

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9/26/17 PHY 133 L69 TA: Li Yabo Friction Lab Report # 3

Introduction:

Friction is a force which happens as a reaction of force and it can be stated as it opposes the motion of the actual force. There are two kinds of friction forces, static and kinetic forces. As it could be known by their names that statics friction is the one which occurs till before an object starts moving, or it occurs till the other force is strong enough to start the motion. Once the motion is started then the force of friction is Kinetic friction. For the lab, we will see as the mass is increased the force of kinetic friction will be counted. The following expression of Force of Friction will be used to carry on our solution. Ff=uFn In this experiment, we will be determining how force of friction changes along with the change in mass and we will be solving the coefficient of kinetic friction between the device and the surface. Procedure: a) 1- Connect the dongle to the computer and turn on the device. 2- Put the screw in to the device and leave it on rest as the y axis is acting upwards. 3- Start recording and after few seconds, lift the device up for few seconds and put it back. 4- Now you have the average force of gravity and acceleration. 5- Find the mass using Fg=mg b) 6789-

Now replace the screw with a plate and put the device wheels up. Give the device a push in y direction by the plate and record. The device comes to rest itself and keep recording it. Now we have the acceleration and friction and we can get them by analysis mode. 10- We have the mass and acceleration of the force of friction after the peak, so we can find the force of friction acting using newtons second law F=ma c) 11- Now using the scotch tape, stick your phone to the device and perform the experiment to calculate mass and acceleration after the peak. 12- Now add another mass on top of it, here we have used a phone and then a calculator and stick them together. 13- Perform the experiment to figure out the mass and the acceleration after the peak. 14- Calculate the force of friction.

Number 1:

Error= 0.044 N 

Average of the Force of gravity is given by u in the upper graph.

Error= 0.015 m/s^2 

Acceleration is given along the y axis in the upper graph.

When device is connected to the plate and given a push. 



When I stopped pushing the device it still has acceleration but that is deacceleration, means as I pushed the device in Y axis, it gained some acceleration and reached the peak as seen in the upper graph, but then after reaching the peak, it started deaccelerating and still had the acceleration but in negative way and the force of friction which is opposing the motion is becoming greater and greater and eventually it comes to a stop. To find the force acting on the device, using the mass and acceleration, we can simply use the analysis mode to find the mean acceleration at the accelerometer.

Error= 0.13 m/s^2 

Average acceleration of the device. It’s the deceleration. This is the acceleration of the force of friction after the peak.

Through Newton’s second law, knowing the acceleration and mass, we can find the force. Number 2:

Error= 0.076 N 

Average force of gravity.

Error= 0.014 m/s^2 

Acceleration of the device along y axis. X and Z axis are close to zero.

Error= 0.058 m/s^2 

The acceleration after the peak which is basically deacceleration or the acceleration of the friction force.

Number 3:

Error= 0.091 N 

This graph shows us the average force of gravity.

Error= 0.0046 m/s^2 

This graph gives us the value for average acceleration along the y axis.

Error= 0.086 m/s^2 

This is the acceleration of force of friction after the peak.

Calculation: Mass number 1: 

To get mass:

Fg=mg (-3.192N)=m(-9.817m/s^2) m= 0.325 kg Mass number 2: 

To get mass:

Fg=mg (-4.522N)=m(-9.820m/s^2)

m= 0.461 kg Mass number 3: 

To get mass:

Fg=mg (-5.876N)=m(-9.824m/s^2) m= 0.598 kg

Force number 1: 

To get force:

Mean acceleration is -2.391m/s^2 And mass we have is M= 0.325 kg F=ma F= 0.325 kg x (-2.391) m/s^2 F= - 0.777 N Force number 2: 

To get force:

Mean acceleration is -1.292 m/s^2 And mass we have is M= 0.461 kg F=ma F= 0.461 kg x (-1.292) m/s^2 F= -0.596 N Force number 3: 

To get force:

Mean acceleration is -1.245 m/s^2 And mass we have is M= 0.598 kg F=ma F= 0.598 kg x (-1.245) m/s^2 F= -0.745 N

Normal force 1: N= mg 0.325x9.80 = 3.185 N Normal force 2 N= mg 0.461x9.80 = 4.518 N Normal force 3 N=mg 0.598 x 9.8= 5.86 N Friction Normal N N -0.777 3.185 -0.596 4.518 -0.745 5.86 Values of u: 1st: Ff=uFn (-0.777N)= ux(3.185N) u= -0.244 2nd Ff=uFn (-0.596 N)= ux (4.518N) U= -0.132 3rd Ff=uFn (-0.745 N)= ux ( 5.86N) u= - 0.127 Average u (-0.244-0.132- 0.127)/3

= -0.168

Results: Gravitational Force N

Gravitational acceleration m/s^2

Mass kg

Force of Friction N

Acceleration of Friction force m/s^2

Normal force N

-3.192N

-9.817m/s^2

0.325 kg

- 0.777 N

-2.391m/s^2

3.185N

-4.522N

-9.820m/s^2

0.461 kg

-0.596 N

-1.292 m/s^2

4.518N

-5.876N

-9.824m/s^2

0.598 kg

-0.745 N

-1.245 m/s^

5.86N

1 2 3

Coefficient of friction -0.244 -0.132 - 0.127

Error bars Fg = Fn 0.044 N 0.076 N 0.091 N

Normal N 7 5.86

6

Normal Force N

4.52

5 4

3.19

3 2 1 -0.8

-0.75

-0.7

-0.65

-0.6

0 -0.55

Friction Force N

Slope= 2.266906

Discussion: The results were as expected that with the increase of mass, the force of friction which is opposing the actual motion increases too. But we had some errors, which came due to table surface and when we added the extra masses and while calculating the masses and acceleration and forces. We had uncertainties. We calculated the mass of the device and then using the Fg=mg, we got the mass of the device. Then by pushing the device by the plate and recording the accelerometer, we got the peaks and acceleration after the peak which was basically the acceleration of the friction force or the deacceleration. Then using Newton’s second law of motion, we found out that F=ma is applicable and we found out the force of friction. Then using the gravitational force we used the expression Ff=uFn, we got the coefficient of friction.

Conclusion: The force of friction shows up as the reaction of force on an object and it opposes the motion with which the actual force started. We come to know that the friction increases as the mass increases. Although friction is not dependable on the mass it depends on the materials which are in contact and the force which is pushing actually the surfaces together....