Physics multiple choice questions

[thisisfreaky]

I'm doing some practice multiple choice questions for my class and I would like to check my answers for some ones I wasn't entirely sure about. Any explanations would be really helpful.
1)What is the acceleration of an object of mass 4.5*10^-5 kg with a charge of 9*10^-9 C under the influence of an electric field of magnitude 5000 V/m assuming gravity is negligible.
A) 0.05m/s^2
B) 0.5m/s^2
C) 0.9m/s^2
D) 1.0 m/s^2
E) 5.0m/s^2
I got choice B.

2) A charged particle is in a region that contains both an electric and a magnetic field. The kinetic energy of the particle is 9 uJ at point X and 11 uJ at point Y. If the only forces present are electromagnetic, what is the work done by the electric force on the particle as it moves from X to Y along a upside down parabolic path?
A)0 uJ
B)1 uJ
C)2 uJ
D) 11uJ
E) 20 uJ
I just sort of guessed C on this one.

An object is placed 12 cm in front of a concave mirror. The mirror forms a real inverted image that is the same size as the object, also at 12 cm in front of the mirror. The focal length of the mirror is
A) 3.0 cm
B) 4.0 cm
C) 6.0 cm
D) 12 cm
E) 24 cm
I guessed choice D on this one.

 

[Redbelly98]

Please show your work or reasoning on how you got your answers. For the ones where you just guessed, try to find what equations would apply.