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Homework Help: Lift force and acceleration

  1. Oct 13, 2009 #1
    1. The problem statement, all variables and given/known data

    Suppose a 66-kg boy and a 42-kg girl use a massless rope in a tug-of-war on an icy, resistance-free surface. If the acceleration of the girl toward the boy is 3.0 m/s2, find the magnitude of the acceleration of the boy toward the girl.

    2. Relevant equations

    Newton's Second Law of Motion?

    3. The attempt at a solution

    I tried to use Newton's Second Law but got a incorrect answer


    A 4570-kg helicopter accelerates upward at 1.8 m/s2. What lift force is exerted by the air on the propellers?
    I did 4570/1.8 =2538.8888 N but that seems too big

    3. An 880-kg (1945 lb) dragster, starting from rest, attains a speed of 26.0 m/s (58.2 mph) in 0.59 s.
    (a) Find the average acceleration of the dragster during this time interval.

    (b) What is the magnitude of the average net force on the dragster during this time?

    (c) Assume that the driver has a mass of 68 kg. What horizontal force does the seat exert on the driver?
    880-68 = 812?
  2. jcsd
  3. Oct 13, 2009 #2


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    Homework Helper

    For the first one, the force pulling the girl is the opposite for the force pulling the boy. Newton's third law. Now use the second law.

    2) Make an equation relating the upward forces and the downward forces and the resultant force it produces.
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