7. a 1.0-kg box accelerates from rest in a straight line across a frictionless surface for 20. s as depicted in the force vs. time graph to the right. (a) find the time taken for the object to reach a speed of 5.0 m/s b)determine the boxes velocity at the 15s time

Since you have not included the experiment situation and the data, of course, i can not give you specific details about it. but i can you with this question.1) i will assume that the motion is projectile (parabolic) motion.2) yes, the horizontal distance depends on the horizontal velocity as, naming vx the horizontal velocity and t the time, it is: x = vx × t3) now, observe that the flight time depends on the vertical velocity as, naming voy the initial vertical velocity, t the time and y the vertical distance before reaching the ground: y = yo + voy×t - gt² / 2.the higher the initial vertical velocity (voy) the longer the object will be flying and so t will be higher in the equation for the horizontal distance.that explains the relationship between the horizontal distance and the horizontal velocity.

The density of the block of iron is lees than the density of mercury but the density of the block of iron is greater than the density of water