1A) If an object is in motion, does that mean that the object has a net force in

Question

1A) If an object is in motion, does that mean that the object has a net force in the direction of that motion? Explain.

1B) Design a simple experiment that you could carry out in your home to:

- determine the coefficient of static friction between an object and a surface.

- prove that the coefficient of static friction is dependent only on the surfaces in contact, and is not affected by any change in the mass of your object.

i) Describe your plan. It must include a list of materials, a diagram of the set-up, and an explanation of the steps you would take and the data you would collect.

ii) Explain how you would analyze the collected data to determine the coefficient of static friction and prove that it is unaffected by any change in the mass of your object.

iii) State one possible source of error that you might encounter in this experiment and state the steps you took to minimize or eliminate this source of error.

1C) Efficient and safe transportation depends on friction being either minimized or maximized, as necessary. Using research, find:

i) one example in which friction is maximized to aid in transportation.

ii) one example in which friction is minimized to aid in transportation.

iii) For each situation, explain how the friction is maximized/minimized and why this is necessary or beneficial.

iv) Give at least one source that you used for your research.

Explanation / Answer

1 A) if an object is in motion, that does not mean that the object has net force in the direction of that motion

this is because an object moving in a prticular direction , but slowing down has a velocity in one direction but acceleration in the opposite direction

and hence a moving object with retarding force is an example of an object having motionand net force in opposite ( different) directions

B) i) materials required:

a. A plank of wood

b. some objects with plane base

c. protractor

Plan : put the object on the plank, and slowly increase the angle of inclination of the plank

stop when the object start to slide slowly and note that angle

ii) from theory we know that this angle is angle of repose

hence tan(theta) = k ( where k is static friction coefficient)

to prove that this force depends only on the surfaces in contact and not on the masses of the objects

stack some object on the reference object on the incline, and we will find out that the angle at which the objects start to move is still the same

iii) sources of error : since this experiment requires a delicate human intervention, there is a scope of human errors inthis experiment

C) i) friction is maximised in case of objects being carried by inclined conveyor belts to prevent objects from slipping

ii) friction is minimised in ball bearings used to assist motion in moving parts

iii) in case 1, friciton is needed to prevent blocks from slipping, in case 2, friction is hampering motion so it is reduced by the use of lubriants

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