14. Jet propulsion in free space operates on the principle of conservation of (a

Question

14. Jet propulsion in free space operates on the principle of conservation of (a) momentum, (b) kinetic energy, (c) mass, (d) none of the p recedi ng 15. You are standing on a skateboard, initially at rest. A friend t hrows a very heavy ball towards you. You can either catch the object or detl object back towards your friend (such that it moves away from you with the same speed as it was originally thrown) . What should you do in order to minimiz (a) Your final speed on the skateboard will be the same regardless whether you catch the ball or deflect the bal1 (b) deflect the ball (c) catch the ball ect the e your speed on the skateboard? 16. A block is moved to the right a displacement ax = s. What can be said about the sign of the work done by the force F? . . (a) It is positive. (b) It is negative. (c) It is zero. (d) There is not enough information to answer the question . 17. What can be said about the work done by force F? (a) It is positive. (b) It is negative. (c) It is zero. (d) There is not enough information to answer the question. 18. What can be said about the work done by force Fr 2 (a) It is positive. (b) It is negative. (c) It is zero. (d) There is not enough information to answer the question. 19. The work produced by a force F moving an object through a displacement Ax is (a) F Ax sine, (b) F Ax tan, (c) F Ax cose, (d) FAt (a) the kinetic energy decreases, (b) the applied force component and displacement are at right angles, (c) the work can't be done, (d) none of the preceding

Explanation / Answer

14) a) momentum

15) c) catch the ball

16) c) It is zero

since, W = F*s*cos(theta)

17) b) It is negative

18) a) It is positive

19) C) F*delta_x*cos(theta)

20) a) The kinetic energy decreases.

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