The 24 N force applies an acceleration <em>a</em>₁ such that
24 N = (8.0 kg) <em>a</em>₁
<em>a</em>₁ = (24 N) / (8.0 kg)
<em>a</em>₁ = 3.0 m/s²
Starting from rest, the object accelerates at this rate for 10 s, so that it reaches a velocity <em>v</em> of
<em>v</em> = (3.0 m/s²) (10 s)
<em>v</em> = 30 m/s
and in these 10 s, the object travels a distance <em>d</em>₁ of
<em>d</em>₁ = 1/2 (3.0 m/s²) (10 s)²
<em>d</em>₁ = 150 m
When it hits the rough surface, it slows to a stop in 10 s, so that its accleration <em>a</em>₂ during this time is such that
0 = 30 m/s + <em>a</em>₂ (10 s)
<em>a</em>₂ = - (30 m/s) / (10 s)
<em>a</em>₂ = -3.0 m/s²
so that it covers an additional distance <em>d</em>₂ such that
<em>d</em>₂ = 1/2 (-3.0 m/s²) (10 s)²
<em>d</em>₂ = 150 m
So the object travels a <em>total</em> distance of <em>d</em>₁ + <em>d</em>₂ = 300 m.
Alternatively, once we find the accelerations during both 10 s intervals and the velocity after the first 10 s, we get
(30 m/s)² - 0² = 2 (3.0 m/s²) <em>d</em>₁
<em>d</em>₁ = (30 m/s)² / (6.0 m/s²)
<em>d</em>₁ = 150 m
and
0²- (30 m/s)² = 2 (-3.0 m/s²) <em>d</em>₂
<em>d</em>₂ = (30 m/s)² / (6.0 m/s²)
<em>d</em>₂ = 150 m
so that, again, <em>d</em>₁ + <em>d</em>₂ = 300 m.