A 1.7 kgkg block slides along a frictionless surface at 1.4 m/sm/s . A second block, sliding at a faster 4.2 m/sm/s , collides with the first from behind and sticks to it. The final velocity of the combined blocks is 2.6 m/sm/s . Part A What was the mass of the second block

Iknow the first part it is the average star i am not 100% sure

Answertraveling around a circular trackexplanation"traveling around a circular track" is the best answer as you could be traveling around a circular track at a constant speed. your velocity would therefore have the same magnitude but will always be constantly direction. since acceleration is the rate of change of velocity, the rate of change will only involve the direction of velocity and not the magnitude.wrong choices: "an object at rest" does not accelerate at all"increasing speed while traveling around a curve" means that the acceleration will not be constant due to only change in direction; it will be constant due to both magnitude and direction"an object in free fall" does not necessarily change direction 

Athermometer to measure the temperature of course