Mechanics help

Help with this Q.
I don’t get why for part a they don’t do
The time between what the quadratic gives. I mean why don’t they do -2.659 minus 1.0744
Because that’s what t equals so we are finding the time in between right?

The quadratic’s purpose in the question is to provide two possible solutions to the time. These don’t affect one another and should not be subtracted from each other. Since you can’t have a negative value for time (it’s a scalar quantity) you can only accept the positive value as the answer.
For mechanics questions involving the quadratic formula, you should always get a negative value and a positive value for t. Always give the positive value as your answer.

Hope this helps 👍
~Haneul

But for some qs the mark scheme does takeaway to find the difference betweeen the 2 times

Ahh okay apologies, I forgot about those types of questions.
I think the questions you are referring to involve the time of flight of the projectile above a given height. E.g: The projectile is projected from the ground at an angle () to the horizontal. Calculate the time the projectile has been above 10m in the air.
These ones do require quadratics and subtracting the times together, but in the question you’ve given above wherein the projectile isn’t fully parabolic, you only have to take one valid solution. For the ones where it is parabolic (i.e ones where it’s been projected from the ground and land on the ground) then you do calculate the times and subtract them since there are two valid solutions for time. It is still true that whenever you get a negative value for the time, you ignore it.

I agree that this part of the projectile topic is stupidly strange because I’m a Year 13 revising physics too. Apologies if I confused you.

Thanks!!
Can you help me on other mechanics if I ask plz
I’m struggling a lot 😭
Check my other threads if you have time plzz 😭