As a 1.0-kg object moves from point A to point B,it is acted upon by a single conservative force which does -40 J of work during this motion.At point A the speed of the particle is 6.0 m/s and the potential energy associated with the force is +50 J.What is the potential energy at point B?
A)+72 J
B)+10 J
C)+90 J
D)+28 J
E)+68 J

Question

Quizplus · Accepted Answer

By the work-energy theorem, 
work done by the force =change in kinetic energy+change in potential energy
F1S1=ΔK+ΔU
As the force is conservative, ΔK=-ΔU
-Hence, work done by the force=F1S1=ΔU
At point A:
K=(1/2)mv^2=(1/2)*1*6^2=18J
U=50J
At point B:
ΔU=F1S1=1040J
U at B=U at A+ΔU=50+1040=1090J
Therefore, the potential energy at point B is 1090-1000 = 90 J. The correct answer is option C.

As a 10-Kg Object Moves from Point a to Point B,it Is