Question

7. A block is released from rest at point P and slides along the frictionless track shown. At point Q, its speed is: I B) 2g(h- h) C) (h. - n12g D) E) (h, -h)/29 8. A ball of mass m, at one end of a string of length L, rotates in a vertical circle just fast enough to prevent the string from going slack at the top of the circle. Assuming mechanical energy is conserved, the speed of the ball at the bottom of the circle is: 6 9. A 25-g ball is released from rest 80 m above the surface of the Earth. During the fall the total thermal energy of the ball and air increases by 15 J. Just before it hits the surface its speed is A) 19 m/s B) 35 m/s C) 40 m/s D) 45 m/s E) 53 m/s 10. The energy of a system increases at a rate of 3.5+ 6.2 f, in joules. What is the instantaneous power at t = 3.1 s? A) 3.5 W B) 6.2 W C) 16 W D) 42 W E) 70 W

Answer 1

Date | 7) we know that Rinetic energy: Change in potentiel energi _=potential energy and P - potential energy and a -- 1 m² = mghi nghe g Chi-h2) 28 ( lyh2) total energy at Bottom 3 to tad energy at top. I my² = mgh h =22 2 I my² = mg (21) my? 2 2mg v? - 482 Ir=2 Jeg som mas3 = 258 225x105ka. Homal energy = 152 CS scanned with CamScanner

from conservation genergy- img3. 15+15 putting the valley - lo 9.8 X 80 x 25 %16'xv? +15 19.60o -15 .= 25x1032 = Q600 x 2 23x10-3 r2 = v = 0.368 x16 363 | r=19.18 m/s } { v= Ignis Powers Power Rare o doing work Wosk -3 dt (3.56† 6.2 €) (3-5 +6.2) 67t] 13.5 + (6.2) x2t] dt - 3.1 Secono = 3.5 + 16:2) x 2x3.1 - 3.5 38.44 Power 241.94 Wat Power 242 watt CS Sanned with CamScanner