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19 Nov 2019

Could someone please help me understand how the Normal Force and the forces in the x- and y-axis are found? I know it has to do with the cosine and sine of an angle, but why? In this problem, how do you know that the angle under the piano is 28? I don't understand the drawing provided with the solution. THANK YOU!

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Sixta Kovacek
Sixta KovacekLv2
12 Oct 2019
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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

Refer to Fig. 5-38. Let the mass of the block be 8.5 kg and theangle θ be 30°. Find (a) the tension in the cord


I know acceleration is zero and it will only be the net force alongthe x-axis and I even get the calculations of the process. What Idon't understand is where the mgsin(θ) comes fromin T - mgsin(θ) = 0 . I know it has to do with thetriangles but i don't see the correlation.

This is probally a moronic misunderstanding on my part andhopefully an easy question to answer, thank you in advance.

(a) What is the weight of a 5.78 kg backpack at the surface ofthe Earth?
56.7 N ( I understand this problem after some time :) )
(b) What is the weight of the same backpack at the surface of theMoon where the acceleration due to gravity is only 1.6 m/s2?
9.37 N (as well as this problem)

(c) If the backpack is atthe surface of the Earth, and if a net force of 8 N is applied tothe backpack, what is the amount of acceleration of thebackpack?
(Not sure here)

m/s^2
I was thinking A = Fnet/m
Fnet being the total force on the object being equal to G(mass ofthe earth)/(radius of the earth)^2
(I know it isn't as simple as adding 8N to the weight of backpackat the surface of the earth, if I divide by the net force thatisn't adding the net force to the weight...Please Help)


(d) If the backpack is atthe surface of the Moon, and if the same net force is applied tothe backpack, what is the amount of acceleration of thebackpack?
(If I don't understand C of course I am confused on this problem aswell, thank you for your help in advance I can figure out where togo with this problem if I understand C)

m/s2
Please explain to me so that I understand for test

Someone posted a response to this earlier but I don't think theanswer was correct... Can someone please take the time to help mecarefully with this? Thanks!

A kayaker can paddle her kayak at a steady 2.5m/s in still water.She wishes to cross a river that is 2000m wide and has a current of-1.5m/s (goes from right to left along x axis). She is crossinggoing "north", along the positive y axis.

(a) IF the kayaker first "aims" her craft straight across theriver, the current will carry her downstream as she paddles across.What will be her actual velocity (magnitude and direction angle) asshe crosses? How long will it take her to cross the river?

(b) If she "aims" the kayak somewhat upstream, she can actuallytravel straight accross the river. In what direction must she aim?What is her actual speed accross the river for this situation, andhow long will it take her to cross?

HINT: The angle found in (a) will NOT be the same angle required inpart (b).

--- I have figured out (a) to be: a velocity of 2.92 m/s at121 degrees (CCW from x axis). I figured it would take 805s tocross (the distance she travels, or the hypotonuse of the triangle,is 2333.27m).
I really need help on part (b) though :(

Is that right? And could someone help me on (b) please? :)

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