# physics (it's rather urgent help is appreciated

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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)

• physics (it's rather urgent help is appreciated - ,

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.

• physics - ,

thank you so much, sorry for being rather spamy so to say

• physics - ,

i can't quite get the value of t

• physics (it's rather urgent help is appreciated - ,

its wrong....

• physics (it's rather urgent help is appreciated - ,

ss01 how do you solve this then

• physics (it's rather urgent help is appreciated - ,

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.

• physics (it's rather urgent help is appreciated - ,

i got it wrong followed your ways

• physics (it's rather urgent help is appreciated - ,

@phy what other questions did you got? i got 1st one

• physics (it's rather urgent help is appreciated - ,

i got all except this one

• physics (it's rather urgent help is appreciated - ,

kyle and ss01 can you please tell me how to solve the 1st problem?

• physics (it's rather urgent help is appreciated - ,

which part?

• physics (it's rather urgent help is appreciated - ,

keep on differentiating and put the time value u vl get it

• physics (it's rather urgent help is appreciated - ,

@kyle could you plz tell me how to do 2 & 3

• physics (it's rather urgent help is appreciated - ,

@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

• physics (it's rather urgent help is appreciated - ,

@ kyle what is the option for 3 question
my radius is 7m and mass is 5kg

• physics (it's rather urgent help is appreciated - ,

plz tell me how to do 5 & 6

• physics (it's rather urgent help is appreciated - ,

@kyle what is for south pole

• physics (it's rather urgent help is appreciated - ,

qustion 3
v=8.366

• physics (it's rather urgent help is appreciated - ,

south pole is 0

• physics (it's rather urgent help is appreciated - ,

ac=v^2/r

• physics (it's rather urgent help is appreciated - ,

@anonymous plz specify

• physics (it's rather urgent help is appreciated - ,

v=sqrt(r*g)

• physics (it's rather urgent help is appreciated - ,

kyle ...got the 2

• physics (it's rather urgent help is appreciated - ,

@anonymous what is the 3rd option for question 3

• physics (it's rather urgent help is appreciated - ,

@Anonymous how do you solve for the 7th question

• physics (it's rather urgent help is appreciated - ,

@kyle did you all the options for 6th one?
i got 1st 2 correct rest all wrong

• physics (it's rather urgent help is appreciated - ,

I didn't get you, can you explain it properly how to do the 1st problem

• physics (it's rather urgent help is appreciated - ,

for acceleration double differentiate the equation. you get only x and y vector left with some constant but no z vector

• physics (it's rather urgent help is appreciated - ,

i didn't got the speed

• physics (it's rather urgent help is appreciated - ,

Well, I don't know how to differentiate, can you explain it to me.

• physics (it's rather urgent help is appreciated - ,

you could search on youtube there are lot of good videos on it. there are various rules too be followed.

• physics (it's rather urgent help is appreciated - ,

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

• physics (it's rather urgent help is appreciated - ,

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

• physics (it's rather urgent help is appreciated - ,

Thanks. Did you get Stone On Roof Find Distance problem?

• physics (it's rather urgent help is appreciated - ,

@kyle did you got angle 0?
337.64 for dis?

• physics (it's rather urgent help is appreciated - ,

no, i think bobpursely was wrong, trying to get a second opinion

• physics (it's rather urgent help is appreciated - ,

• physics (it's rather urgent help is appreciated - ,

anyone for stone off a cliff question help?

• physics (it's rather urgent help is appreciated - ,

@ss01 for what question

• physics (it's rather urgent help is appreciated - ,

i got all except for stone on roof, find distance

• physics (it's rather urgent help is appreciated - ,

anyone any luck?

• physics (it's rather urgent help is appreciated - ,

@ss01 did you manage to find the time?

• physics (it's rather urgent help is appreciated - ,

@anon for which question?

• physics (it's rather urgent help is appreciated - ,

@ss01 for the inclined wall stone throw

• physics (it's rather urgent help is appreciated - ,

i didn' t got that, the 2nd last question right?

• physics (it's rather urgent help is appreciated - ,

yeah

• physics (it's rather urgent help is appreciated - ,

did you got the hw3 question5 & 7

• physics (it's rather urgent help is appreciated - ,

no