Equations of uniformly accelerated motion
3 marks · NormalA tennis ball is thrown vertically upwards with an initial speed of 18 m/s. It decelerates at 10 m/s² due to gravity until it stops momentarily at its highest point.
Explain, using the suvat equation, how you would calculate the maximum height reached by the ball.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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Must show: States final velocity at max height is 0 m/s, Selects and rearranges correct equation, Mentions substitution of values for calculation
Also accept: Using v = u + at to find t first, then using s = ut + 0.5at^2
Common mistakes: Incorrect sign for acceleration; Incorrectly using initial velocity as zero
Show mark scheme and worked solution
Marking points
B1 · 1 mark · States final velocity at maximum height is 0 m/s.
M1 · 1 mark · Chooses correct suvat equation, e.g., v^2 = u^2 + 2as, and rearranges for s.
M2 · 1 mark · Describes or shows substitution of values to calculate maximum height.
Worked solution
At the maximum height, the ball's velocity is 0 m/s. The equation v^2 = u^2 + 2as can be used, where v = 0, u = 18 m/s, a = -10 m/s².
Rearrange to find s: 2 × (-10) × s = -324 s = 324 / 20 = 16.2 m