[Year 12 Maths] Mechanics - Resisted Motion -Getting stuck on the past part (part iv) -Please help!

[katsicum]

Hi there, I am so close to getting over this question but unfortunately I am still getting stuck on the last part. I have tried to a lot of ways but none has worked out. Attached below are the question along with my full working out for the previous parts respectively. Thank you so so much for helping me! Also the answer is 27%

 

[HallsofIvy]

We are told that "x is the height of the particle above its point of projection" but what is \(\displaystyle \over{x}\) used in the formula?

 

[Harry_the_cat]

It's x with 2 dots above. Second derivative w r t time. In other words, acceleration.

 

[HallsofIvy]

Too early in the morning! Thanks!

 

[katsicum]

We are told that "x is the height of the particle above its point of projection" but what is \(\displaystyle \over{x}\) used in the formula?

As mentioned in #3, that sign is indeed acceleration )