4) Which of the following statements is always true? A) if a system of two parti

Question

4) Which of the following statements is always true?

A) if a system of two particles has a total momentum of zero, it also has a total kinetic energy of zero.

B) if a system of two particles has total kinetic energy of zero, it also has a total momentum of zero.

C) both of these statements are always true

D) neither of these statements is always true

5) a forklift moves a 100 N box at a constant speed from one shelf 1 meter high to another shelf 10 meters away at the same height. How much work did the forklift do on the box?

A) less than 100 J, but more than 0 J

B) 100 J

C) more than 100 J

D) zero

Explanation / Answer

4)   If total kinetic energy is zero , than velocities must also be equal to zero .

Thus, B) if a system of two particles has total kinetic energy of zero, it also has a total momentum of zero.

5) As, Work done = F * s * cos(theta)

                                = 100 * 10 * cos90

                                 = 0 J

Thus, work did the forklift do on the box = zero .

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