SOLUTION: There are 2 cars moving in opposite directions. the distance between them is 300cm. They move forward for 100 cm with a speed of 50 cm/s, and comes back 50 cm at 25 cm/s. After how

Question 887059: There are 2 cars moving in opposite directions. the distance between them is 300cm. They move forward for 100 cm with a speed of 50 cm/s, and comes back 50 cm at 25 cm/s. After how many seconds will the cars collide ?
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
100 cm at 50 cm/s = 2 seconds
50 cm at 25 cm/s = 2 seconds
the solution depends on whether you consider a touch a collision.

if you do consider a touch a collision, then they collide in 6 seconds.
each car will travel 100 cm in 2 seconds.
each car will go back 50 cm in 2 seconds.
after 4 seconds they will be at the 50 cm mark.
each car then travels another 100 cm in 2 seconds.
they have both traveled 150 cm at the 6 second mark.
since both meet at the 150 cm mark, you can consider this a collision but it would not be a very severe one.
they would just touch.

if you don't consider a touch a collision, then they collide in 9 seconds.
each car will travel 100 cm in 2 seconds.
each car will go back 50 cm in 2 seconds.
after 4 seconds they will be at the 50 cm mark.
each car then travels another 100 cm in 2 seconds.
they have both traveled 150 cm at the 6 second mark.
the cars would touch at the 150 cm mark, but you do not consider this a collision so they continue on their way.
they go back 50 cm in the next 2 seconds.
they are now at the 100 cm mark in a total of 8 seconds.
they attempt to move forward 100 in the next 2 seconds, except that they never get there because they collide at the 150 cm mark.
it took them both 1 second to get to the 150 cm mark from the 100 cm mark, so they collide after 9 seconds total.

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