Question 408134

You can calculate the {{{constant}}} force restricting motion from the first part of the question, where he slows down without braking. 


First convert the given speed to {{{m/s}}}:

{{{u = 36 (1000/3600) = 10 m/s}}}}

{{{v = 0}}}

{{{s }}}= ?
{{{a }}} =?
{{{t = 25s}}}


{{{v = u + at}}}

{{{0 = 10 + 25a}}}

{{{-25a = 10}}}

{{{a = -10/25}}}

{{{a = -0.4 m/s^2}}}


{{{F = ma}}}

{{{F = 320 (-0.4)}}}

{{{F = -128 N}}}

So there is a force {{{resisting}}} motion with a magnitude of {{{128 N}}}. Next calculate his {{{acceleration}}}:


{{{u = 0}}}

{{{v = 126 * (1000 / 3600) = 35 m/s}}}

{{{s}}} =?

{{{a}}}=?

{{{t = 6s}}}


{{{v = u + at}}}

{{{35 = 0 + 6a}}}

{{{a = 35/6}}}

{{{a = 5.833 m/s}}}

Now calculate the {{{force}}}{{{ required}}} to give him this {{{acceleration}}}, remembering that there's a resistive force in play which we'll call {{{R}}}:

{{{R + F = ma}}}

{{{F = ma - R}}}

{{{F = 320 * 5.833 - (-128)}}}

{{{F = 1,866.667 + 128}}}

{{{F = 1994.667}}}

{{{F = 1995 N}}}


So the engine supplies a carrying force of {{{1995 N}}}.