PhysicsLAB: 2002 B5

AP Free Response Question
2002 B5

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A proton of mass m_p and charge e is in a box that contains an electric field E, and the box is located in Earth’s magnetic field B_Earth. The proton moves with an initial velocity v vertically upward from the surface of Earth. Assume gravity is negligible.

	(a) On the diagram above, indicate the direction of the electric field inside the box so that there is no change in the trajectory of the proton while it moves upward in the box. Explain your reasoning.

	(b) Determine the speed of the proton while in the box if it continues to move vertically upward. Express your answer in terms of the fields and the given quantities.

The proton now exits the box through the opening at the top.

	(c) On the figure above, sketch the path of the proton after it leaves the box.

	(d) Determine the magnitude of the acceleration a of the proton just after it leaves the box, in terms of the given quantities and fundamental constants.

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