Deck 7: Interactions

Question 1

A 2.0 kg mass is moving along the x-axis. The potential energy curve as a function of position is shown in the figure. The kinetic energy of the object at the origin is 12 J. The system is conservative,and there is no friction.
(a) What will be the kinetic energy at 2.0 m along the +x-axis?
(b) What will be the speed of the object at 6.0 m along the +x-axis?

Answer 1

(a)24 J
(b)2.2 m/s

Question 2

Is it possible for a system to have negative potential energy?

A) Yes, as long as the kinetic energy is positive.
B) Yes, as long as the total energy is positive.
C) Yes, since the choice of the zero of potential energy is arbitrary.
D) No, because the kinetic energy of a system must equal its potential energy.
E) No, because this would have no physical meaning.

Answer 2

Yes, since the choice of the zero of potential energy is arbitrary.

Question 3

Consider the motion of a 1.00-kg particle that moves with potential energy given by
U(x)= (-2.00 J∙m)/x + (4.00 J∙m²)/x². Suppose the particle is moving with a speed of 3.00 m/s when it is located at x = 1.00 m. What is the speed of the object when it is located at x = 5.00 m?

A) 2.13 m/s
B) 3.00 m/s
C) 4.68 m/s
D) 3.67 m/s

Answer 3

3.67 m/s

Question 4

A 2.00-kg object traveling east at 20.0 m/s collides with a 3.00-kg object traveling west at 10.0 m/s. After the collision,the 2.00-kg object has a velocity 5.00 m/s to the west. How much kinetic energy was lost during the collision?

A) 0.000 J
B) 458 J
C) 516 J
D) 91.7 J
E) 175 J

Question 5

A baseball is thrown vertically upward and feels no air resistance.As it is rising

A) both its momentum and its mechanical energy are conserved.
B) its momentum is not conserved, but its mechanical energy is conserved.
C) both its momentum and its kinetic energy are conserved.
D) its kinetic energy is conserved, but its momentum is not conserved.
E) its gravitational potential energy is not conserved, buts its momentum is conserved.

Question 6

A 2.0-kg object is moving without friction along the x-axis.The potential energy curve as a function of position is shown in the figure,and the system is conservative.If the speed of the object at the origin is 4.0 m/s,what will be its speed at 7.0 m along the +x-axis?

A) 4.0 m/s
B) 4.2 m/s
C) 4.4 m/s
D) 4.6 m/s
E) 9.8 m/s

Question 7

On a smooth horizontal floor,an object slides into a spring which is attached to another mass that is initially stationary.When the spring is most compressed,both objects are moving at the same speed.Ignoring friction,what is conserved during this interaction?

A) momentum and mechanical energy
B) momentum only
C) kinetic energy only
D) momentum and kinetic energy
E) momentum and potential energy