Answer :
The final velocity after 6.0 s is
1304.2 .
What is velocity?
velocityis the most fundamental quantity of physics . Work is said to be done when a force applied to an object cause a displacement of a object.
Solution -
As per the given-
Mass of runner m = 74kg
initial velocity of runner u=4.8 m/s
final velocity of runner v =0
Coefficient of friction ¥=0.7
Let's d be the distance moved by runner till the stop.
a- mechanical energy lost due to friction
As friction does negetive work causing the runner to stop.
As we know,
Mechanical energy lost= Kinetic energy of runner
Mechanical energy lost =
1/2 mv^2 = 1/2 ×74×4.8^2=852.2
Distance move by runner-
Work done by friction = mechanical energy lost
-¥×mg×d =852.2 j
-0.7×74×9.8×d = -491.2
Solving the equation we get
1304.2.
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