Question

A 150-kg object takes 1.5 minutes to travel a 2,500-meter straight path. It begins the trip traveling 120 m/s and decelerates to a velocity of 20 m/s. What was its acceleration?

Answer 1

Okay. The basic thing we will use here is the work energy theorem.
See, if you calculate the change in Kinetic energy, it will be equal to the work done by the force which is decelerating the object.
\[1/2 m v _{2}^{2} - 1/2m v _{1}^{2} = F \times s\]
where v1 and v2 are final and initial velocities respectively.
After we have the force, by newtons 2nd law,
\[F = ma\]
Thus, we will get a negative acceleration ( same as a positive deceleration ). I got the answer to be -2.8. Please recheck by putting the values, Im very messy with calculations. :)