Need help understanding what is going on for part A 1.) the question just ask fo
ID: 1274628 • Letter: N
Question
Need help understanding what is going on for part A
1.) the question just ask for the position of the sand bag, so why are they caluating the final velocity of the bag at .250s ?
2.) I thought that the gravity is pushing down on things, so if someone throught a bag up in the air the acceleration should be -9.81 if that is tru then if someone drops a bag 40m in the air the accel should be positive right?
A hot-air balloonist, rising vertically with a constant velocity of magnitude v = 5.00m/s , releases a sandbag at an instant when the balloon is a height h = 40.0m above the ground . After it is released, the sandbag is in free fall, (a) Compute the position of the sandbag at a time 0.250s and 1.00 s after its release, (b) How many seconds after its release will the bag strike the ground? (c) With magnitude of velocity does it strike the ground? (d) What is the greatest height above the ground that the sandbag reaches? Sketch ay -1, vy -1 and y -1 graphs for the motion.Explanation / Answer
1) It is not for the part (a) , at last in the question they ask to draw the vy-t graph of the motion , so to draw this we have to know the points , that's why the calculate to illustrate that at t=0.250s it is still going upwards according to the person in ground which your frame of reference, because from ground you are measuring the height velocity and acceleration not from the person in ballon.
2) Acceleration due to gravity is always negative (towards the ground) whether it is drop from the ballon or throw upwards , it doest not depends on the object initial velocity whether it is drop or thrown upwards. Here they have taken the upwards direction as positive so acceleration is always in the negative y-direction.
Suppose the acceleartion is positive when it drops that it means it velocity should be increased upward be because acceleration is rate of change of velocity. If it is positive that means rate of change is positive that gives the final velocity increasing. If this is the case then bag will never come to ground , it goes into the space.
So acceleration is negative no matter whats the velocity direction.