The image you uploaded shows a physics problem related to a rock being thrown upward on Mars. To help solve the problem, I would need the initial velocity of the rock, which isn't visible in the screenshot. I will outline the steps to solve each part based on the typical physics equations for projectile motion.

Assuming the acceleration due to gravity on Mars is $g = 3.71 \, \text{m/s}^2$ (which is approximately true), here’s how we can approach the questions:

(a) Find the velocity after 2 seconds

The velocity of the rock at any time $t$ can be found using the equation: $v(t) = v_0 - g \cdot t$ where:

• $v_0$ is the initial velocity (unknown from the image, but necessary),
• $g$ is the acceleration due to gravity on Mars ($g = 3.71 \, \text{m/s}^2$),
• $t = 2$ seconds.

(b) Find the velocity at time $t = a$

This is a general form of the same equation for velocity: $v(a) = v_0 - g \cdot a$ where $a$ is a variable time. You would need to plug in the value of $a$ when given.

(c) When will the rock hit the surface?

The rock will hit the surface when its displacement $s = 0$ (assuming it returns to the same height from