An inclined plane ends into a vertical loop of radius r as shown in figure. If a particle of mass m is released from topmost point. The point C on the track as shown in the figure and centre of circular tack are at same horizontal level. The normal force at point C is-
A)8 mg
B) 7 mg
C)1 mg
D)3 mg
Correct Answer:
A
Solution :
Apply energy conservation b/w highest point & pt C, \[mg\times 4r=\frac{1}{2}m{{v}^{2}}\] \[v=\sqrt{8gr}\] \[N\,\,=\,\frac{m{{v}^{2}}}{R}\,\,at\,\,po\operatorname{int}\,\,C\] \[N\,\,=\,\,8mg\]