39. Calculate the recoil velocity of a 5-kg rifle that shoots a 0.02-kg bullet at a speed of 620 (m/s).
(A)-10 m/s
(B) -5 m/s
(C) -2.5 m/s
(D) -1,25 m/s
(E) -1 m/s

35. A 5.0-kg block moves with velocity v = 3.0i + 5.0j(m/s) on a horizontal surface of coefficient of kinetic friction μ = 0.30, where i and J are unit vectors that point along tiie x and、coordinate axes, respectively. When the block comes to rest, what is the total thermal ehei^y increased? (A)1.2x 102J (B)63 J (C) 38 J (D)26J (E)85 J

36. A wheel rotates initially at a rate of 10 rad/s and begins to accelerate at a rate of 2 rad/s2. After 3 seconds the rate of the rotation will be (A) 6 rad/s (B) 9 rad/s (C) 10 rad/s (D) 16 rad/s (E) 19 rad/s

37. A force-tune curve for a ball struck by a bat is shown in the figure. What is the impulse on the ball?(A) 12000 (N●s) (B) 6000 (N●s) (C) 3000 (N●s) (D)6(N●s) (E) 3 (N●s)

38. A force of 20 N acts on a wagon at an angle of 30° to the ground. Calculate the work done by the force Wien the wagon is dragged 100 m along the ground.(A) 600 J (B) 800 J (C)100J (D) 1300 J (E) 1700 J

40. Neglect the friction and weights of pulleys and cord in the figure. The body of mass m2 is falling down with acceleration a2 = g/2. What is the mass ratio m2/m1? (A)1 (B)3/2 (C)2 (D)5/2 (E)4

41. A block of mass m was placed on a surface (coefficient of kinetic friction μ) with an inclined angle θ. The block is initially moving uphill with speed v. What is the total distance dtiie block moves before the block goes downhill or stops?  (A)(B)(C)(D) (E)

42. A uniform stick 1.0 m long with total mass 15 kg rests on a firictionless table and is pivoted at its end. The uniform stick rotates freely about this pivot. A bullet with a mass of 10 g and a speed of400 m/s strikes the center of the stick, in a direction perpendicular to tiie stick and embeds itself there. Find the stick' s angular speed. (A) 0.1 rad/s (B) 0.4 rad/s (C) 0.6 rad/s (D) 02 rad/s (E) 0.8 rad/s 

43. One quarter of a circular loop of wire carries a current I. The current I enters and leaves on straight segments of wire. The straight wires are along tiie radial direction ftom the center of the circular portion, Find the magnetic field at the center of tiie circular. (A) (B) (C)(D)(E)

44. A capacitor C is fully charged by a de power supply so that one plate has charge Q0. It is disconnected from the power supply and is connected to a inductor L, which results in an electrical oscillation. What is the angular frequency ω of the oscillation and its maximum current I0? (A)(B)(C)(D)(E)

45. What is the average translational kinetic energy of molecules in an ideal gas at 37°C? (A) 1.3x10-21 j (B) 2.6x10-21 j (C)4.2X10-21J (D) 5.2x10-21j (E) 6.4x10-21 J