19. After a snowstorm, you put on your frictionless skis and tie a rope to the back of your friend’s truck. Your total mass is 70 kg and the truck exerts a constant force of 20 N. How fast will you be going after 15 seconds, in m/s and MPH?


  1. Explanation:

    It is given that,

    Total mass is 70 kg

    The truck exerts a constant force of 20 N.

    Then the net force is given by :

    F = ma

    a is acceleration of rider

    a=\dfrac{F}{m}\\\\a=\dfrac{20}{70}\\\\a=\dfrac{2}{7}\ m/s^2

    Initial velocity of rider is 0. So, using equation of kinematics to find the final velocity as :

    v=u+at\\\\v=at\\\\v=\dfrac{2}{7}\times 15\\\\v=4.28\ m/s

    Since, 1 m/s = 2.23 mph

    4.28 m/s = 9.57 mph

    So, the speed of the rider is 4.28 m/s or 9.57 mph.  


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