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Investigation 3 - For the weekly lab report
Everyday Physics (PHYS1110)
University of New South Wales
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Investigation 3: Static Friction Aim of the investigation: This investigation aims to determine the coefficient of static friction between an object and the angle of a slope for which the object starts to descend. The subsequent goals are to be able to separate forces into components, as well as grasping the concept of Newton’s second law and frictional forces. Collaboration This investigation was performed by me alone. Faqrull Imran Zainal Abidin (z5096394) Group F Risk Assessment In order to minimize risk towards myself and my surroundings, I have conducted the experiment under the guidelines of the risk assessment below. Hazards Tasks (Step 3) Existing risk controls (Step 5) (Step 4) Stones falling to the floor Injury from stepping on the stones; possible tripping Adjusting ramp’s angles Collapsing the setup Injury from fallen ramp/anything on the ramp – bruises and light trauma Setting box on ramp Box falling from Improper placement Impact from fallen object causes injury Placing stones inside box Risk rating with existing controls * Associated risks C L R Insert stones inside the box with care Instantly pick up fallen stones Wear appropriate footwear 2 C M • • Using both hands to setup Ensure footing of the ramp is stable 2 C M • Place the box at appropriate location (e. at the center of the edge) 1 D L • • • Setup Pictures below show the setup of this experiment. A different box is set underneath the ramp to give it elevation. This box will be moved while keeping the ramp’s end part (the one touching the ground) at a constant location, to adjust the ramp’s angle. To reduce the parallax error in reading the protractor, I ensured that my eyesight was parallel to the protractor. Results *Mass of box = 0 Mass (kg) Uncertainty in mass (kg) Angle 1 (o) Angle 2 (o) Angle 3 (o) Average angle (o) Uncertainty in angle (o) 0 0 33 30 31 31 1 0 0 33 30 29 30 2 0 0 31 30 29 30 1 0 0 32 30 32 31 1 0 0 29 31 30 30 1 5. This experiment shows that the coefficient of static friction (𝜇𝑠 ) does not depend on the object’s mass. We know that 𝐹𝑑𝑜𝑤𝑛 is equal to 𝐹𝑓𝑟 , and 𝐹𝑑𝑜𝑤𝑛 is equal to the coefficient of static friction times 𝐹𝑁 . Thus: 𝐹𝑑𝑜𝑤𝑛 = 𝐹𝑓𝑟 𝐹𝑑𝑜𝑤𝑛 = 𝜇𝑠 ∗ 𝐹𝑁 𝑚 ∗ 𝑔 ∗ sin(𝜃) = 𝜇𝑠 ∗ 𝑚 ∗ 𝑔 ∗ cos(𝜃) 𝜇𝑠 = sin(𝜃) = tan(𝜃) cos(𝜃) Since we can explain the 𝜇𝑠 without requiring the 𝑚, result is consistent with the theory 6. Coefficient of Static Friction vs Mass of Object 0 Coefficient of Static Friction ( μs) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Mass of Object (Kg) The graph above agrees with the expectation that the mass does not affect the coefficient of static friction. The coefficient moves up and down around the same area of value regardless of the change in mass. Conclusions The experiment conforms the theory that the coefficient of static friction is not dependent on the mass of an object. Even with different masses, the angles required for the box to move are approximately similar. Other factors such as texture of surface area might be the defining component in the coefficient of static friction.
Investigation 3 - For the weekly lab report
Course: Everyday Physics (PHYS1110)
University: University of New South Wales
