Unformatted text preview: Unit 3 Problem Set Key
Ranking Tasks Section:
RT I.
I wo asteroids with masses of w and 3m exert gravitational forces on each other. A student contends that the forces
will be in different directions and of different magnitudes as shown below.
Planet A
Planet B
What's wrong. if anything, with this student's contention? If something is wrong. identify it and explain how
to correct it. If this student's contention is correct. explain why.
Answer: The forces are attractive so the directions should be reversed and the forces should be equal as required
by Newton's Third Law.
Planet A
Planet B
RT 2.
Three objects each with a mass of M exert gravitational forces on each other, Which of the
arrows below shows the direction of the net force on mass IT
B
(iv)
(v) None of these
OC
Explain your reasoning
Answer (a) vector addition of the force ou B by A (which is directed horizontally to the left) and the force on $ by
C (which is directed toward the bottom of the page or down) results in a force 45" down to the left
RT 3,
Object A has twice the mass of Object B.
Identify the pair of force vectors (the arrows) that correctly compare the gravitational
force exerted on A by B with the gravitational force exerted on B by A.
Gravitational force on A by B Gravitational force on B by A
(b)
(d)
(el
Explain your reasoning.
Answer: (by
The forces must be attractive, because the gravitational force is always an attractive force. Newton's Third Law
requires that the magnitude of the forces be the same....
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- Fall '18
