please do them correctly Multiple choice Questions (5 points each, total 20 poin

Question

please do them correctly

Multiple choice Questions (5 points each, total 20 points) 1) A stone is tied to a string and whirled around in a circle at uniform speed. Select the correct statement from below. 2. The work done by the string on the stone is positive b. The work done by the string on the stone is negative The work done by the string on the stone is zero d. None of these 2) You are walking up an inclined ramp. Now, select the correct statement a. Friction does positive work on you b. Friction does negative work on you C. Friction does zero work on you d. None of these 3) For each case shown below, the mass is released from rest at the top and feels no friction or air . resistance. Now choose the correct choice a. Maximum Speed: case (c), Maximum work done on the mass: case (c) b. Maximum Speed: same for all, Maximum work done on the mass: case (c) C. Maximum Speed: same for all, Maximum work done on the mass: case (a) d. Maximum Speed: case (b), Maximum work done on the mass: case (b) Maximum Speed: case (b), Maximum work done on the mass: case (c) La unuecar

Explanation / Answer

1. (c) The work done by the string on the stone is zero. work done = F.dcos(theta) . Here displacement is perpendicular to the force ( which is towards the center) therefore zero work done since cos 90 = 0

2 . (b).This depends on the frame of reference. Friction always acts in the direction opposite to the direction of motion therefore it does negative work with respect to the moving object. Angle between force and displacement is 180 degree. cos 180 = -1 .Therefore negative work.

3. Question is incomplete.

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.