practice q's 2

# practice q's 2 - Mid-Term Practice Please also review class...

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Mid-Term Practice Please also review class notes and Homework question set A nice tutorial on all questions of interest to us so far is also at hyperphysics web site http://hyperphysics.phy- astr.gsu.edu/hbase/hframe.html under mechanics, heat, and thermodynamics sections.

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Q • Outline the key steps of the scientific method. Please explain the meaning of each term in plain language.
a 1. Recognize/Observe a question or a problem or a phenomenon 2. Make an educated guess- a hypothesis - as to the answer 3. predict the consequences that should be observable if the hypothesis is correct and that should be absent if the hypothesis is incorrect 4. perform the experiment to verify if the predicted consequences are present 5. formulate the simplest general physical law that organizes the above ingredients optional 6. assemble laws into a scientific theory meaning of each term (observation, hypothesis, experiment, and physical law) such as embedded above is sufficient. e.g., hypothesis - educated guess observation - generally accepted fact experiment - method to test the prediction physical law - the general formulation of the result

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Q • A ball is rolling across a pool table and slowly stops. (a) how would Galileo interpret this observation ?(b) how would Aristotle interpret this observation ? (c) In your estimation, what are the forces acting on the ball, if any ?
a (a)Galileo: Force of friction resisted the inertial motion (b)Aristotle: Without a persistent force, the ball will assume its natural position of rest. (c)The force of friction is resisting the rolling motion, thus decelerating the ball. The ball is also acted upon by equal and opposite forces on it because of its weight and the normal force from the pool table.

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q Two automobiles with equal and opposite momenta have a head-on collision and comes to rest. Is their momentum conserved ? Is their kinetic energy conserved ? Explain your answers.
a • Yes for momentum. Initial momentas are +p and –p. Thus, net initial momentum is same as the final momentum. • No. Their final kinetic energies are zero. Initial KINETIC ENERGIES (scalars) are frictionally dissipated- for instance as heat and sound.

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Q Q8. Can an object reverse its direction of travel while maintaining (a) a constant acceleration; (b) a constant speed; and (c) a constant velocity ? Please explain your answer.
a Yes for (a) and (b) No for (c). Constant velocity requires constant speed and direction of travel. Hence no.

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Q • When the velocity of a car travelling on a leveled road is doubled, which of the following statements are true. (a) its acceleration doubles
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## practice q's 2 - Mid-Term Practice Please also review class...

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