A block travels either of the paths shown. The surface is frictionless. The hori
ID: 2077388 • Letter: A
Question
A block travels either of the paths shown. The surface is frictionless. The horizontal distance from the start to the end of each of the ramps is the same. The following two questions apply to this diagram. MI) pts) For which case is the block traveling fastest when it leaves the end of the ramp? A) I B) II C) It is traveling at the same speed in either case. D) none of the above is correct. M2)3 pts) For which case when it leavesthe end ofthe ramp? A) I B) II C) It is traveling at the same speed in either case. D) none of the above is conrect. M3 (4 pts) A woman holds a bowling ball in a fixed position. The work she does on the ball A) depends on the weight of the ball. B) depends on how long she holds the ball. C) cannot be calculated without more information. D) is equal to zcro.Explanation / Answer
The block is under effect of gravity which is a conservative force.It means the work done by it is independent of path taken i.e. the work done will depend upon final and initial positions only.As in the given question initial(y1) and final positions(y2) are same for both conditions so we can apply law of conservation of energy to get speed at final point y2.
Note.The block is also acted upon by normal force which is perpendicular to direction of displacement;the angle between force and displacement is 90°.
So work done by normal force is zero(Work done=force x displacement x cos(angle between force and displacement). Normal force is an example of non conservative force.
mg(y1)=mg(y2) +(mv^2)/2f
=>v ={mg(y2-y1)}^(1/2).
Answer M1---(C) speed is same in both cases.
M2-----(C) speed is same in both cases.
M3----(D) work done s zero.It is because work done is equal to force muliplied by displacement caused by force.Since woman is just holding the ball there is no diplacment observed the work done is zero.
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