A few problems on "MOTION IN ONE DIMENSION" INTRODUCTION: Here are a problem on "Motion in one-dimension". THE PROBLEMS: (1) "Car A is just behind Car B.Both are 5m long.The velocity of A is 15 m/s while that of B is 10 m/s. Find the road distnace covered by Car A to cross Car B." WHAT MY BRAIN SUGGESTED: Let's say Car B moves 'x' distance in time t. So, for Car A to cross Car B, it has to move by a distance of 'x+10' in the same time interval t (since Car A has to move an extra distance of the sum of its own length and that of Car B, so as to cross Car B). So, the equation that stands is x/10 = (x+10)/15. Thus from this equation, x is 20. So, road distance covered by Car A is x+10= (20+10)= 30m. WHAT MY BOOK SAYS: The answer given in my book is 35m. But i don't know how! WHAT I WANT TO KNOW: I just wanna know the flaw in my calculation. To me, my method seems allright.But why is the answer not matching? THE PROBLEMS (Contd.): (2) "A police jeep is chasing with 45 km/h.A thief in another jeep is moving with 155km/h. Police fires a bullet with muzzle velocity 180m/s. Find the velocity with which the bullet strikes the jeep of the thief." WHAT MY BRAIN SUGGESTED: How is it possible to find the final velocity without knowing the distance travelled? I mean the problem doesn't give the initial distance between the two jeeps. ***ERROR PROCESSING*** BRAIN CANNOT SUGGEST ANYTHING***INSUFFICIENT DATA FOR MY BRAIN. WHAT MY BOOK SAYS: The solution of this problem is given in my book. It says: "V= v(police) + v(bullet) - v(thief). Putting the values and changing km/h to m/s, the answer given is 150m/s. WHAT I WANT TO KNOW: How do we get the above formula(the one given in my book)? CONCLUSION: Hey, I'm really confused. Any help will be appreciated. Thanks a lot.