Two identical balls are thrown directly upward, boll A at speed v and boll B at

Question

Two identical balls are thrown directly upward, boll A at speed v and boll B at speed 2v. and they feel no air resistance. Which statement about these balls is correct? A) Ball B will go twice as high as ball A because it had twice the initial speed. B) Ball B will go four times as high as ball A because it had four times the initial kinetic energy. C) The balls will reach the same height because they have the same mass and the same acceleration. D) At its highest point, ball B will have twice as much gravitational potential energy as ball A because it started out moving twice as fast. E) At their highest point, the acceleration of each ball is instantaneously equal to zero because they stop for an instant. 9) A traveler pulls on a suitcase strop at an angle 30degree above the horizontal. If 1200 J of work are done by the strap while moving the suitcase a horizontal distance of 15 m. what is the tension in the strap? A) 75 N B) 61 N C) 85N D) 92N E) 55 N 10) A 2.0 kg mass is moving along the x-axis. The potential energy curve as a function of position is shown in the figure. The kinetic energy of the object at the origin is 8 J. The system is conservative, and there is no friction. What will be the kinetic energy at 2.0 m along the +x-axis? A) 24J B) 12J C) 20J D) 2.2J E) -24 J

Explanation / Answer

height reached by ball A = v^2 / 2g

height reached by ball B = (2v^2) / 2g = 4v^2 / 2g

so ball B will go Four times high than the Ball A

option B is correct

9) let the tension in the strap be T

work will only be done by the horizontal force

so W = F*S

1200 = T cos a*S

1200 = T*cos 30 *15

T = 92.37 N

10) Total energy at origin = total energy at x = 2.0m

22 + 8 = KE + 10

KE = 20 J

option C is the correct answer

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