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Homework Help: Basic conversion help

  1. Aug 29, 2009 #1
    1. The problem statement, all variables and given/known data
    a. if you square the accleration expressed in meters per second per second, in what unites will the answer be expressed?
    b. if you divide momentum measured in N*s (1 N = 1 kg*m/s^2) by a speed expressed in meters per second, in what units will the answer be expressed?
    c.a billionaire offers $1.4 billion if you will first count the amojnt in $1 bills or a lump sum of 5000 (assume you can count an average of 1 bill per second, and be sure to allow for the fact that you will need about 10 hours per day for sleeping and eating. how long will it take to count the amount in $1 bills?
    d. one cubic cm (1.0 cm^3) of water has a mass of 1.0 x 10^-3 kg. determine the mass of 8.0 m^3 of water.

    3. The attempt at a solution
    a. no idea
    b. m/s^2 / m/s = m(s)/m(s^2) = 1/s .... said seconds but apparently incorrect

    c. 1400000000=3600 bills/hour(time) - 10 hrs/day .... t=388889 hours + 10 hrs/day = 16204 days + 10 hrs/day ; 10 hrs/day x 1 day/24 hours =.417 days; 16204 (.417)= 6757 days; 16024 days + 6757 days = 22961 days x 1 yr/365 days = 63 years (wrong as well)

    d. 1 m= 100 cm ; 8m (100 cm/m) = 800 cm ; 800 cm (.001 kg/cm)=.8 kg (wrong)

    help is greatly appreciated thanks!
  2. jcsd
  3. Aug 29, 2009 #2


    Staff: Mentor

    When you multiply or divide units, they behave the same as ordinary algebraic expression.
    a) If the acceleration was measured in miles/(hour ^2), the square of this unit would be miles^2/(hour^4)
    [tex]\frac{kg~m}{s^2}/ \frac{m}{s}~=~\frac{kg~m}{s^2} * \frac{s}{m}~=~? [/tex]

    d) 1m = 100 cm, so 1 m^3 = 100^3 cm^3 = 1,000,000 cm^3
    8 cubic meters of water would have a mass vastly larger than .8 kg.
    Last edited: Aug 29, 2009
  4. Aug 29, 2009 #3
    thanks but a was still wrong, as was B which i put kg/s.....i finished the last one and got 1000 kg which was also wrong
  5. Aug 30, 2009 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    What was your answer, and how did you get it? Just saying "I got it wrong" gives us no clue how to help you out.

    The question is asking you to take the square of (m/s^2). Mark44 provided an example using different units.

    That answer is indeed wrong. Perhaps start out by giving 1 N in terms of m, kg, s.

    Next, multiply by s to give 1 N*s in terms of m, kg, s.

    Finally, divide by m/s to get the final answer.

    Please show us your work.
  6. Aug 30, 2009 #5
    sorry i dont really understand what you advised me to do for B...as for A and D, i ran out of try attempts for webassign so those are hopeless now. can anyone help me with the billionaire question im really struggling on this and need all the points i can get.
  7. Aug 30, 2009 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Start out by writing 1 N in terms of m, kg, s.
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