Question

A smooth sphere (mass 10 kg, negligible radius) moves on a smooth curved surface from the point with a speed of 10 m/s as shown in figure. The sphere reaches the point D passing through point B. If the ground is taken as reference, Then $[g=10m/s^2]$

• A. The total mechanical energy of the sphere at point A is zero
• B. The total mechanical energy of the sphere at the point A is 2500 J
• C. The kinetic energy at point B is 2500 J
• D. The potential energy at point B is 0J

Answer 1

Answer: (B), (C), (D)

The correct options are
B The total mechanical energy of the sphere at the point A is 2500 J
C The kinetic energy at point B is 2500 J
D The potential energy at point B is 0J

(B) Energy at A = $\frac{1}{2}m{v}^2+mgh$

$\frac{1}{2}\times 10\times 100+10\times 10\times 20$

= 500 + 2000

$=2500J$

(C) Now energy conservation from A to B

$\frac{1}{2}m{v}^2+mgh$ = K.E

2500 = K.E

(D) Potention energy is zero at ground level

Hence option (B)(C)(D) are correct