2023TrialShort answer

Q21 (a)

1 mark

Question

The diagram below shows the H-shaped posts used in a game of rugby.
The path of a ball that is kicked and just passes over the crossbar is shown below.
The initial velocity of the ball is $20.0\ \mathrm{m\,s^{-1}}$ at an angle of $40.0^\circ$ to the ground. The top of the crossbar is $3.00\ \mathrm{m}$ above the horizontal ground. Ignore the effect of air resistance and treat the ball as a simple projectile.

(a) Determine the minimum velocity of the ball in flight.

Uncropped source page 13 for question 21.a; requires human review and cropping — Reviewed visual · source page 13

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Solution

Marking Criteria	Marks
• Correct calculation for the horizontal component of the initial velocity	1

Minimum velocity = horizontal component of the initial velocity at maximum height.

v_{\min} = v\cos 40^\circ = 15.3\ \mathrm{m\,s^{-1}}

Supplied marking guidance · human reviewed

Compare this with your working, not only your final sentence.

Syllabus alignment

Module 5 · Advanced Mechanics

Projectile MotionRelate launch velocity and angle to maximum height, flight time, final velocity and horizontal range using equations of motion.
Projectile MotionResolve projectile motion into horizontal and vertical components, assuming constant gravitational acceleration and negligible air resistance.

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