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Posted by on Saturday, October 5, 2013 at 5:01pm.

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 - , Saturday, October 5, 2013 at 5:34pm

    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 - , Saturday, October 5, 2013 at 5:45pm

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

  • physics - , Saturday, October 5, 2013 at 6:13pm

    i can't quite get the value of t

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 12:37am

    its wrong....

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 5:35am

    ss01 how do you solve this then

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:16am

    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 - , Sunday, October 6, 2013 at 6:17am

    i got it wrong followed your ways

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:19am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:41am

    i got all except this one

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:44am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:45am

    which part?

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:47am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:48am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:52am

    @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 - , Sunday, October 6, 2013 at 6:54am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:56am

    plz tell me how to do 5 & 6

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:57am

    @kyle what is for south pole

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:57am

    qustion 3
    v=8.366

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:58am

    south pole is 0

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 6:58am

    ac=v^2/r

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:00am

    @anonymous plz specify

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:01am

    v=sqrt(r*g)

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:05am

    kyle ...got the 2

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:07am

    @anonymous what is the 3rd option for question 3

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:12am

    @Anonymous how do you solve for the 7th question

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:13am

    @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 - , Sunday, October 6, 2013 at 7:33am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:35am

    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 - , Sunday, October 6, 2013 at 7:37am

    i didn't got the speed

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:39am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 7:40am

    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 - , Sunday, October 6, 2013 at 7:47am

    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 - , Sunday, October 6, 2013 at 7:59am

    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 - , Sunday, October 6, 2013 at 8:01am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 8:02am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 8:02am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 8:05am

    @KYLE plz reply

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 8:10am

    anyone for stone off a cliff question help?

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 8:16am

    @ss01 for what question

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 8:18am

    i got all except for stone on roof, find distance

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 9:24am

    anyone any luck?

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 9:34am

    @ss01 did you manage to find the time?

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 9:50am

    @anon for which question?

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 10:04am

    @ss01 for the inclined wall stone throw

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 10:09am

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

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 10:24am

    yeah

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 11:21am

    did you got the hw3 question5 & 7

  • physics (it's rather urgent help is appreciated - , Sunday, October 6, 2013 at 11:37am

    no

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