First we calculate the acceleration of the cart:
a = (v₂ - v₁) / (t)
a = (7 m/s - 3 m/s) / (8 s)
a = 4 m/s / 8 s
a = 0.5 m/s²
Using the Newtons Second Law:
F = m×a
F = (10 kg)(0.5 m/s²)
F = 5 N
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