physics model answer needed..
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anyone can kindly provide a model answer for this??
thx in adv! -
1. The graph will be a curve with an inital positive gradient. However, as time passes by, the gradient of the graph decreases down till 0 when the line becomes a horziontal line at time t.Originally posted by Fireindahouse:
anyone can kindly provide a model answer for this??
thx in adv!
For acceleration vs time graph, assume that the air resistance is directly proportional to the velocity of the feather.
For acceleration vs time graph, it will be a straight diagonal line with a negative gradient from y- intercept a which represents the initial acceleration of the feather to the y- axis.
Air resistance is directly proportional to the velocity of the object. Imagine, as the feather is increasing speed due to the presence of gravitational force acting on it. However, in the presence of still air, as velocity of the feather increases, air resistance also increases. Hence, the resultant force decreases.
Rmb F = ma. Thus, the resulting acceleration of the feather decreases until the resultant force is 0. In that case, I can say that the feather have attained terminal velocity. At this state, the gravitational force acting on the feather is the same as its air resistance.
Idea is roughly like that. Please check on my grammar. -
a) Use air resistance to answer. Explain that terminal velocity occurs when upward force = downward force, hence net force = 0. By newton's 2nd law, there will be zero acceleration, and by newton's 1st law, the feather will continue at a constant velocity (terminal velocity)Originally posted by Fireindahouse:
anyone can kindly provide a model answer for this??
thx in adv!
b) Moon got air a not? -
moon gravitational pull 1.6m/s..
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Moon doesn't have any atmosphere. This means that there is nothing on the moon to retain the air. Thus, on the surface of the moon, it is vacuum.
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curve is for a velocity time graph.Originally posted by tanjun:1. The graph will be a curve with an inital positive gradient. However, as time passes by, the gradient of the graph decreases down till 0 when the line becomes a horziontal line at time t.
For acceleration vs time graph, assume that the air resistance is directly proportional to the velocity of the feather.
For acceleration vs time graph, it will be a straight diagonal line with a negative gradient from y- intercept a which represents the initial acceleration of the feather to the y- axis.
Air resistance is directly proportional to the velocity of the object. Imagine, as the feather is increasing speed due to the presence of gravitational force acting on it. However, in the presence of still air, as velocity of the feather increases, air resistance also increases. Hence, the resultant force decreases.
Rmb F = ma. Thus, the resulting acceleration of the feather decreases until the resultant force is 0. In that case, I can say that the feather have attained terminal velocity. At this state, the gravitational force acting on the feather is the same as its air resistance.
Idea is roughly like that. Please check on my grammar.
but i dont understand the acceleration time graph. i know that in the end at terminal velocity there would be no acceleration. But how do you know acceleration is decreasing before it reaches terminal velocity? -
basically as the feather/object falls, 2 forces act on it. taking away from the planet as positive, the mass+ the gravitational attraction causes a decceleration force of F1=mg.
the 2nd force is that of air resistance/friction which causes acceleration. that is related to the velocity of the feather/object by the equation F2 = -kv or -kv^2
and the acceleration is determined by the resultant of the 2 forces. therefore as |v| (speed) increases, the F2 and the acceleration increases until equilibirum.