Asked by anon

We are standing at a distance d=15 m away from a house. The house wall is h=6 m high and the roof has an inclination angle β=30 ∘. We throw a stone with initial speed v0=20 m/s at an angle α= 35 ∘. The gravitational acceleration is g=10 m/s2. (See figure)

(a) At what horizontal distance from the house wall is the stone going to hit the roof - s in the figure-? (in meters)


b) What time does it take the stone to reach the roof? (in seconds)

Answered by bobpursley
height of roof: 6+ slope*(distance-15)
slope=sin30 notice distance is the horizontal distance from the wall. distance=vo*cos35*timeinair you know vo, given.

so using that height funcion,

hf=heightof roof=voSin35*time-4.9t^2
or
[6+ sun30*(distance-15)]*=
6+ sun30*(20*cos35*t -15)=20cos30*t-4.9t^2

solve for time in air, t. That is when it hits the roof.

Now, putting that into the horizontal distance equation: 20*cos35*t

check my thinking. Have fun.

Answered by anon
thank you so much, sorry for being rather spamy so to say
Answered by anon
i can't quite get the value of t
Answered by ss01
its wrong....
Answered by kyle
ss01 how do you solve this then
Answered by Phy
Even I wanted to know how to solve this problem.

Can any one tell me how to solve the first problem of the exam?

I got the answers of all problems except these 2.
Answered by ss01
i got it wrong followed your ways
Answered by ss01
@phy what other questions did you got? i got 1st one
Answered by kyle
i got all except this one
Answered by Phy
kyle and ss01 can you please tell me how to solve the 1st problem?
Answered by kyle
which part?
Answered by ss01
keep on differentiating and put the time value u vl get it
Answered by ss01
@kyle could you plz tell me how to do 2 & 3
Answered by kyle
@ss01 if you check homework 2 the 2nd last question it shows you how to do question 2.
for quetion 3 Ac must be 10m/s
so you get 10=v^2/r and from there you can solve since i don't know what value of r you got
Answered by ss01
@ kyle what is the option for 3 question
my radius is 7m and mass is 5kg
Answered by Anonymous
plz tell me how to do 5 & 6
Answered by ss01
@kyle what is for south pole
Answered by Anonymous
qustion 3
v=8.366
Answered by Anonymous
south pole is 0
Answered by Anonymous
ac=v^2/r
Answered by ss01
@anonymous plz specify
Answered by Anonymous
v=sqrt(r*g)
Answered by ss01
kyle ...got the 2
Answered by ss01
@anonymous what is the 3rd option for question 3
Answered by kyle
@Anonymous how do you solve for the 7th question
Answered by ss01
@kyle did you all the options for 6th one?
i got 1st 2 correct rest all wrong
Answered by Phy
I didn't get you, can you explain it properly how to do the 1st problem
Answered by ss01
for acceleration double differentiate the equation. you get only x and y vector left with some constant but no z vector
Answered by ss01
i didn't got the speed
Answered by Phy
Well, I don't know how to differentiate, can you explain it to me.
Answered by ss01
you could search on youtube there are lot of good videos on it. there are various rules too be followed.
Answered by Phy
Can you tell me how to calculate distance of the particle to the origin at time, speed of the particle and the smaller angle? I got the acceleration. Thanks
Answered by kyle(PLS HELP )
distance is the magnitude of the position vectors
speed is the magnitude of the velocity vector and
for the angle its the z vector for velocity divided by the magnitude of the velocity
Answered by Phy
Thanks. Did you get Stone On Roof Find Distance problem?
Answered by ss01
@kyle did you got angle 0?
337.64 for dis?
Answered by kyle(PLS HELP )
no, i think bobpursely was wrong, trying to get a second opinion
Answered by ss01
@KYLE plz reply
Answered by ajay
anyone for stone off a cliff question help?
Answered by ss01
i got all except for stone on roof, find distance
Answered by ss01
anyone any luck?
Answered by ss01
@anon for which question?
Answered by ss01
i didn' t got that, the 2nd last question right?
Answered by anon
yeah
Answered by ss01
did you got the hw3 question5 & 7
Answered by anon
no
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