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Physics book slides off a horizontal 
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#1
Sep804, 12:40 AM

P: 35

A physics book slides off a horizontal table top with a speed of 1.60m/s . It strikes the floor after a time of 0.440s . Ignore air resistance.
the following are given: v(0)=1.60 t= 0.440s ok this is the question Find the height of the table top above the floor. Take free fall acceleration to be g=9.80m/s^2 . i need to use this formula: x(t) = x(0) + v(0)t + 1/2at^2 < height formula the thing is why is v(0)t equal to zero? isnt the v(0) given in the problem? i know the correct answer and i know how the book done it, but they dont explain why v(0)t is equal to zero. x(0) = 0 + 1/2(9.8m/s^2)(.440s)^2 < i dont get why v(0) is zero 


#2
Sep804, 01:13 AM

P: 35

ok for that question the answer is 0.949m, so you dont have to do the calculations.
im working on this question: Find the vertical component of the book's velocity just before the book reaches the floor. express in m/s wouldnt it just be distance/time? 0.949m/0.440 = 2.15 which is incorrect 


#3
Sep804, 01:51 AM

P: 525




#4
Sep804, 10:02 PM

P: 35

Physics book slides off a horizontal
do i need the formula.... Vfy = V(0)y  gt v = (9.8)(0.44) = 4.321 which is wrong, why is that? 


#5
Sep804, 10:30 PM

Sci Advisor
HW Helper
P: 3,144

Bonus question:
Does the book land face up or face down? :) 


#6
Sep904, 02:31 AM

P: 525

[tex]v_f = v_i + a\Delta t[/tex] vi is simply zero since book slides off horizontally (with no initial vertical velocity.) [tex] \Delta t [/tex] is simply the time of flight. You got the wrong answer because you added in another minus sign that didn't need to be there. Hope I helped! 


#7
Sep904, 02:37 AM

P: 525




#8
Sep904, 11:05 AM

Sci Advisor
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P: 3,144




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