Ask Experts Questions for FREE Help !
Ask
    addie0305's Avatar
    addie0305 Posts: 1, Reputation: 1
    New Member
     
    #1

    Dec 14, 2007, 04:08 PM
    time and velocity equations
    A mountain climber stands at the top of a 70.0m cliff hanging over an ocean. The climber throws thwo stones vertically 1.5s apart and observes that they cause a single splash when they hit the water. The first stone has an initial velociy of +2.0m/s
    How long after the reliease of the first stone will the two stones hit the water?
    What is the initial velocityt of the second stone?

    I have no idea how to do this! Please help
    jiten55's Avatar
    jiten55 Posts: 105, Reputation: 8
    Junior Member
     
    #2

    Dec 14, 2007, 05:20 PM
    Let initial velocity be u.

    s = ut + 1/2 ft^2 (f = acceleration) (Equation A)

    In case of the first stone, the above is:

    70 = 2t +1/2 g t^2 (g = 9.81) Eqauation C

    Find value of t from above.

    t =3.57

    For the second stone, time = t - 1.5 =2.07

    From equation A

    70 = u 2.07 + 1/2 g 2.07^2

    u = 24 (Approx)

    ANSWER:

    Initial velocity of second stone = 24
    Time = 3.57
    Physics Goddess's Avatar
    Physics Goddess Posts: 6, Reputation: 2
    New Member
     
    #3

    Dec 14, 2007, 07:32 PM
    Set up a table for both of the stones. (This table works for any free-fall problem by the way)

    stone 1:
    y(initial)= 70 m (since it starts at the top of the cliff)
    y(final)= 0 m (since it ends at the bottom of the cliff)
    v(initial)= +2 m/s (Since it is a + velocity it means it was thrown upward)
    v(final)=?
    a= -9.8 m/s^2 (this is always true near the Earth's surface and the object is in free-fall)
    t= t1 (some unknown time, but I will label it t1)

    stone 2:
    y(initial)= 70 m (since it starts at the top of the cliff)
    y(final)= 0 m (since it ends at the bottom of the cliff)
    v(initial)=?
    v(final)=?
    a= -9.8 m/s^2 (this is always true near the Earth's surface and the object is in free-fall)
    t= t1-1.5s (since stone 1 is thrown first, and both stones hit the water at the same time, then the second stone must be in the air 1.5s less than the first stone.)


    Now for each stone you can use your kinematic equations to solve for your unknown stuff. You should be able to solve for all the stuff for stone 1 first, then move on to stone 2

    These tables are a good way to organize the information given to you.

Not your question? Ask your question View similar questions

 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Rewrite equations as balanced chemical equations [ 8 Answers ]

Magnesium chloride yield sulfur dioxide Calcium carbonate yields calcium oxide plus carbon dioxide Nitrogen plus hygrogen yield ammonia Hydrochloric acid plus sodium hydroxide yield sodium chloride plus water

"air time" and velocity of object thrown upwards [ 2 Answers ]

A ball is thrown vertically upwards with an initial velocity of 27.0 m/s. Neglecting air resistance, how long is the ball in the air? What is the greatest height reached by the ball? And calculate the first time when the ball has half of its initial velocity. Thank you!

Sound velocity [ 2 Answers ]

http://www.geocities.com/nk7jaffna/askmehelpdesk/xxx.doc Please open web link for full details Speaker transmit 1000Hz sine wave signal. If vehicle is not move, human heard 1000Hz frequency.

Velocity [ 1 Answers ]

The orbit of Halley's Comet around the Sun is a long thin ellipse. At its aphelion (point farthest from the Sun), the comet is 5.1 1012 m from the Sun and moves with a speed of 12.0 km/s. What is the comet's speed at its perihelion (closest approach to the Sun) where its distance from the Sun is...


View more questions Search