David C. answered • 01/17/21
Enthusiastic, patient, and effective tutor.
Hello Rahul,
From your question it looks like you actually have a better understanding than you realize. The only issue I can see is in the second formula. Perhaps this is what is causing your confusion.
The second formula you gave is (x1+x2)/(t1+t2). The source of confusion may be in the notation as this formula is usually written as (d1+d2)/(t1+t2). The reason for using 'd' instead of 'x' in this formula is because it is used when you have multiple distinct distances that correspond to multiple time intervals.
For example, suppose we travel 5 meters in 7 seconds. then some time goes by and we travel 3 meters in 8 seconds. Using these distinct distances and time intervals we would use the formula
- (d1+d2)/(t1+t2)
- =(5+3)/(7+8) = 8/15 = 5.3 m/s
Your explanation for the first formula (x2-x1)/(t2+t1) and the third formula (v1+v2)/2 are pretty accurate.
Hope this was helpful in clearing up your confusion.
David
David C.
Correct. The formula to use would be (d1+d2)/(t1+t2) where d1=(30)(3)=90 and d2=(40)(2)=80 and so we get the magnitude of the average velocity is (d1+d2)/(t1+t2) = (90+80)/(3+2) = 170/5 = 34Km/h. You can still use (x1+x2)/(t1+t2) it is just more common to use d1+d2 for the numerator to avoid confusing this formula with the formula (x2-x1)/(t2-t1)01/17/21
Rahul A.
see in this problem below here i used x1+x2/t1+t2. A car moves with velocity of 30km/hr for 3 hrs and then moves with velocity of 40km/hr for 2 hrs what is magnitude of average velocity? i calculated x1 and x2 like this x1=v1t1 and x2=v2t2. According to the data here the formula x2-x1/t2-t1 cannot be used i guess.01/17/21