Asked by Abdela said yimer
An object of mass m moving with initial speed of 15 m/s got an acceleration of 10 m/s^ after a constant force F is applied to it. How long does it take for the object to reach 90 meters from its initial position?
Answers
Answered by
drwls
With acceleration of 10 m/s^2,and initial velocity of 15 m/s, the displacement from initial position is
X = 15 t + 5 t^2
If X = 90,
5t^2 + 15t -90 = 0
t^2 + 3t -18 = 0
(t+6)(t-3) = 0
The positive solution is t = 3 seconds. Ignore the negative solution; it is outside the domain of the function.
X = 15 t + 5 t^2
If X = 90,
5t^2 + 15t -90 = 0
t^2 + 3t -18 = 0
(t+6)(t-3) = 0
The positive solution is t = 3 seconds. Ignore the negative solution; it is outside the domain of the function.
Answered by
Sami
S=Ut+1/2at^2
90=15t+1/2(10)t^2
90=15t+5t^2
90/5=15t/5+5t^2/5
18=5t+t^2
(t+6)(t-3)
t=-6 t=3
So the time does not be negative so the answer is t=3
90=15t+1/2(10)t^2
90=15t+5t^2
90/5=15t/5+5t^2/5
18=5t+t^2
(t+6)(t-3)
t=-6 t=3
So the time does not be negative so the answer is t=3
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