Two cars moving in the same direction have speeds of 100 kmh\(^{-1}\) and 130 kmh\(^{-1}\). What is the velocity of the faster car as measured by an observer in the slower car?
30 kmh-1
130 kmh-1
200 kmh
230 kmh-1
Explanation
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Discussions (28)
According to addition of vector; to add a speed to a speed me merely sum up the two magnitude to obtain a speed.this is because speed is a scalar:100kmhr+130kmhr=230.coz they are in the same direction.130-100=30,different direction.so d answer shud be 230km/hr.Answer this
the answer is wrong, when two forces are acting in the same direct the vectors are added but when they are in opposite we subtract... if I am wrong you can correct me
I agree with my school because the difference arises because relative velocity is a measure of how one object "sees" another. In the same direction The relative velocity decreases because the objects are moving along together. In opposite directions:
The relative velocity increases because they are moving toward or away from each other at a combined rate.
so its quite opposite to addition and subtraction of vectors
Since the cars are moving in the same direction you should add the two velocities not subtract. Am I correct?
I concur with myschool. Note the Rule: when a vehicle move in same direction ⬆️ ⬆️ the two bodies should be positive when and when they move in opposite direction ⬇️⬆️ then one body will be positive and the other negative please read this⚠️ then the formula to use is Vab = Va - Vb where "a" is the fast one and "b" is the slow one. Now applying the rule I gave you they are in the same direction ⬆️⬆️ so we have V130,100= (+130)-(+100) = +30 in the direction of the fastest one
