In this question use g=9.8g = 9.8g=9.8 m s−2^{-2}−2
A ball is projected vertically upwards from ground level with speed u u\,u m s−1^{-1}−1.
The ball is modelled as a particle moving freely under gravity.
The ball is more than 20 metres above the ground for a total time of at least 2 seconds.
Show that the ball is more than 20 metres above the ground for a total time of u2−3924.9\dfrac{\sqrt{u^2 - 392}}{4.9}4.9u2−392 seconds.
Hence find the set of possible values of uuu.
265 exam-style questions on AQA A Level Maths 3.2 Q: Kinematics, covering 3.2.1 Language of kinematics, 3.2.2 Graphs in kinematics, 3.2.3 Constant acceleration formulae, 3.2.4 Calculus in kinematics (A-level only), and 3.2.5 Motion under gravity and projectiles (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.