Investigation 3: Static FrictionIntroductionTo do this experiment, the angle that makes an object to move down a slope needs to be measured first. Then, the coefficient of static friction between the surface and the object and the slope can be calculated. By doing this experiment, there should be a clear understanding of separation forces into components, frictional forces and Newtons second law.

Risk assessmentTasksHazards(Step 3)Associated risks(Step 4)Existing risk controlsRisk rating with existing controls *(Step 5)

CLR

Adjust the angleThe wood ramp may fall down

Foot get hurt

Ensure that wood is hold tight1BM

Adjust mass by adding stones Stones may fall all over the floorGet hurt by step on the stonesOnce stones fall down, pick them up as soon as possible3DM

I agree to follow the risk control methods and do the experiment under a safe situation.

By following the procedures, the result is listed below:

Mass (kg)Uncertainty in mass (kg)Angle 1 (o)Angle 2 (o)Angle 3 (o)Average angle (o)Uncertainty in angle (o)*

0.0150.0005242223230.5

0.0700.0005242325241

0.1250.0005252225241.5

0.1800.0005222321221.5

0.2350.0005232024222

Analysis:

Coefficient of static friction is equal to the tangent of the angle at which the objects slide, therefore s =tan ()

Masscoefficient of static frictionOverall coefficient of static friction

0.015tan23 tan0.5 = 0.420.01(tan23+ tan 24+ tan 24+ tan 22+ tan22)/5= tan23

(tan0.5+tan1+tan1.5+tan1.5+tan2)/5= tan1.3Therefore s = tan23 tan1.3=0.42 0.02

0.070tan24 tan1 = 0.450.02

0.125tan24 tan1.5 = 0.450.03

0.180tan22 tan1.5 = 0.400.03

0.235tan22 tan2 = 0.400.03

Question 1

Question 2The net force is zero due to the reason that the objective is static.

Question 3Fdown = mg*sin () =0.015*10*sin (23) = 0.059N

Question 4FN= Fperp= mg*cos () = 0.015*10*cos (22) = 0.139N

Question 5According to this experiment, the coefficient of static friction does not depend on the mass of the object. And the results from this experiment consistent with the theory.

Fdown= FfrFdown= s * FN, so mg*sin () =s *mg*cos () Therefore s = tan ()

Conclusion

According to this experiment, there is a better understanding about separating forces into components, frictional forces and Newtons second law. Also, the mass of an object does not affect the coefficient of static friction.