3. A jumbo jet taxes down the runway, accelerating at a rate of 7.4 m/s2 until it reaches its take-off velocity of 81 ms. If the jet begins from rest, how long will it take to reach its take-off velocity of 81 m/s?

Velocity is the speed of an object in a certain direction so you'd need to know speed and direction

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 

Answerthe distance between the two ends of the galaxy is 150,000 light years;