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mia_material_x1
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Homework Statement
A net horizontal force F=A+Bt^3 acts on a 2kg object, where A=5N and B =2N/s^3. What is the horizontal velocity of this object 4 seconds after it starts from rest?
Homework Equations
F=ma
The Attempt at a Solution
F=ma=5N+(2N/s^3)t^3
(2kg)a=5N+(2N/s^3)(4s)^3 ==> a= 2.5N + t^3 = 66.5m/s^2
a=dv/dt ==> v=(2.5 N)t + (1/4 N)t^4
when t= 4s
V= (2.5)(4) +(1/4)(4)^4 = 74m/s
I used V=Vi+at when Vi=0m/s, t=4s, a=66.5m/s^2, and I got V=266m/s
Which one is correct way of solving it, and why? Please let me know. Thanks