A system of three objects

3objectsNewton2LawA system is composed of three objects with masses m, 5m and 6m. The coefficient of kinetic friction between the objects m, 5m and the surface is 0.5. Find the acceleration of the objects.
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A horizontal net force is applied to a vehicle. Energy. Power. Question 1

Question. Source. Yahoo! Answers !

A horizontal net force of 2000 N is applied to a vehicle of mass 400 kg which is initially at rest on a horizontal surface. Determine ?

a. The acceleration of the vehicle.
b. The kinetic energy of the vehicle 5s after the force is first applied
c. The total power developed 5s after the force is first applied
Solution.

a) Newton’s Second Law F=m*a
So, a = F/m = 2000 / 400 = 5 m/s^2

b) V = Vi + a * t = 0 + 5*5 = 25 m/s
Ek = m * v^2 / 2 = 400 * 25^2 / 2 = 125000 J

c) P – Power = the change of the kinetic energy divided by time
P = (Ek – Eki) / t = 125000 / 5 = 25000 Watt

Thank you!