Answer:
F=m(11.8m/s²)
For example, if m=10,000kg, F=118,000N.
Explanation:
There are only two vertical forces acting on the rocket: the force applied from its thrusters F, and its weight mg. So, we can write the equation of motion of the rocket as:

Solving for the force F, we obtain that:

Since we know the values for a (2m/s²) and g (9.8m/s²), we have that:

From this relationship, we can calculate some possible values for F and m. For example, if m=10,000kg, we can obtain F:

In this case, the force from the rocket's thrusters is equal to 118,000N.
Lower resistivity means higher conductivity: among these materials, the best conductor is silver, therefore it must be the material with lowest resistivity among those. We can also have a look at the value of resistivity of the different materials listed in the problem, to check our answer. The resistivities of the materials are the following:
Wood:

Salt water:

Silver:

Lead:

<span>We see that the material with lowest resistivity among those is silver, therefore the correct answer is silver.</span>
Working...
length of wire L = 1.5 m
current I = 7 A
potential difference V = 68 Volt
According to Ohm's Law
V = IR
R = V/I
R = 68/7
R = 9.7 Ω