This question involves the concepts of the equations of motion.
It took him "1.4 s" to stop.
In this scenario, we will use the first equation of motion to find out the time taken by the sled to stop.
[tex]v_f=v_i+at[/tex]
where,
[tex]v_f[/tex] = final velocity of the sled = 0 m/s
[tex]v_i[/tex] = initial velocity of the sled = 282 m/s
a = decceleration = - 201 m/s²
t = time taken = ?
Therefore,
[tex]0\ m/s=282\ m/s + (-201 m/s^2)t\\\\t=\frac{282\ m/s}{201\ m/s^2}[/tex]
t = 1.4 s
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