iPad 1:05 PM 79%- 2. U/t points I Previous Answers CJSO GP090 My Notes Ask Your
ID: 1997611 • Letter: I
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iPad 1:05 PM 79%- 2. U/t points I Previous Answers CJSO GP090 My Notes Ask Your The figure shows a 0.32-kg block sliding from A to B along a frictionless surface. When the block reaches B, it continues to slide along the horizontal surface BC where the kinetic frictional force acts. As a resut, the block slows down, coming to rest at C. The kinetic energy of the block at A is 19 , and the heights of A and B are 12.0 and 7.0 m above the ground, respectively. 12.0 m -7.0m ic 7.0m Concepts (i) Is the total mechanical energy of the block conserved as the block goes from A to B? es O No Why or why not?( all that O Gravity is a nonconservative force. The net work done by external nonconservative forces is not zero. O The net work done by external nonconservative forces is zero. O The normal force acts perpendicular to the displacement of the block. O Gravity is a conservative force. The normal force acts parallel to the displacement of the block. (ii) When the block reaches point B, has its kinetic energy increased, decreased, or remained the same relative to what it decreased O remained the same Give a reason for your answer. (Select all that apply.) O The total mechanical energy is constant as the block goes from A to B. O Since the potential energy increases, the kinetic energy decreases. O Energy is transformed from potential into kinetic energy. O Energy is transformed from kinetic into potential energy. O The total mechanical energy decreases as the block goes from A to B. O The total mechanical energy increases as the block goes from A to B. O Since the potential energy decreases, the kinetic energy increases. (ili) Is the total mechanical energy of the block conserved as the block goes from B to C? No
Explanation / Answer
(i) Yes
Net workdone by external nonconservative forces is zero.
(ii).Kinetic energy is increased.
Since total energy at point A is equal to total energy at point B
From figure potential energy at point A is greater than potential energy at point B.
(iii).No
friction is nonconservative force.and the net work done by external conservative forces is not zero.
(iv) kinetic energy at point B is K = kinetic energy at A +potential energy at point A - potential energy at point B
=19 J + mghA - mghB
=19 J + mg(hA-hB)
= (19 J) +(0.32 x9.8x(12-7))
= 19J +15.68 J
= 34.68 J
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