Question

1. Two protons  are held in place on the x-axis, one at x = + 4 cm and the other at x= - 4 cm.  A third proton is brought in and placed on the y-axis at y = + 4 cm.

The force exerted on the third proton

		makes an angle of 135 degrees relative to the positive x direction
		makes an angle of 45 degrees relative to the positive x direction
		points in the positive y direction
		points in the negative y direction

2. Two protons  are held in place on the x-axis, one at x = + 4 cm and the other at x= - 4 cm.  An electron is brought in and placed on the y-axis at y = - 4 cm. The potential energy of the electron

		is positive
		cannot be calculated since the kinetic energy of the electron is not given
		is zero
		is negative

Answer 1

Question 1

The force exerted by the first proton on the third proton will have a vertical component along the Y-axis, and a horizontal component along the negative X-axis.The force exerted by the second proton on the third proton will have a vertical component along the Y-axis, and a horizontal component along the positive X-axis. The horizontanl component of each will cancel out, being oppposite in sign, while the component along the Y-axis will add up. Hence , the final force will point in the positive Y-direction.

The third option is correct.

Question 2

The potential at the spot under consideration will be positive, as it is due to two positive charges. Since potential energy is given by , the potential of the negatively charged electron will be negative.

The fourth option is correct.