I. (a) A virtual image is located 30 cm behind a concave mirror with a focal len
ID: 1519605 • Letter: I
Question
I. (a) A virtual image is located 30 cm behind a concave mirror with a focal length of magnitude 20 cm. Where is the object?
(b) A 1.5 µC charge moving at 200 m/s experiences a magnetic force F = (3.0 xˆ + 7.0 yˆ) µN in a magnetic field B = (42 xˆ 18 yˆ) mT. What is the angle between the particle’s velocity and the magnetic field?
(c) (3 points) The resistance of a bagel toaster is 12.0 . The toaster requires 1.00 minutes to completely toast a bagel. If the toaster is plugged into a 110 VRMS outlet, how much energy must toaster consume in order to toast a bagel?
Explanation / Answer
a) f = 20 cm
do = 30 cm
1/f = 1/do + 1/di
1/20 = 1/30 + 1/di
di = image distance = 60 cm
b) The magnitude of the force is |F| = qv |B| sin
where is the angle < 180 degrees between the velocity and the magnetic field.
|F| = sqrt(3^2 + 7^2) = 7.615 µN
|B| = sqrt(42^2 + (-18)^2) = 45.7 mT
7.615*10^-6 = 45.7*10^-3*1.5*10^-6 * 200*sin
sin = 0.555
= 33.7 deg
c) Power = V^2 / R = 110^2 / 12 = 1008.3 J/s
Energy = Power * Time = 60500 J