1991 Paper 2 Q11

Year: 1991
Paper: 2
Question Number: 11

Course: LFM Pure and Mechanics
Section: Projectiles

Difficulty: 1600.0 Banger: 1500.0

Problem

The Ruritanian army is supplied with shells which may explode at any time in flight but not before the shell reaches its maximum height. The effect of the explosion on any observer depends only on the distance between the exploding shell and the observer (and decreases with distance). Ruritanian guns fire the shells with fixed muzzle speed, and it is the policy of the gunners to fire the shell at an angle of elevation which minimises the possible damages to themselves (assuming the ground is level) - i.e. they aim so that the point on the descending trajectory that is nearest to them is as far away as possible. With that intention, they choose the angle of elevation that minimises the damage to themselves if the shell explodes at its maximum height. What angle do they choose? Does the shell then get any nearer to the gunners during its descent?

No solution available for this problem.

Rating Information

Difficulty Rating: 1600.0

Difficulty Comparisons: 0

Banger Rating: 1500.0

Banger Comparisons: 0

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The Ruritanian army is supplied with shells which may explode at any
	time in flight but not before the shell reaches its maximum height.
	The effect of the explosion on any observer depends only on the distance
	between the exploding shell and the observer (and decreases with distance).
	Ruritanian guns fire the shells with fixed muzzle speed, and it is
	the policy of the gunners to fire the shell at an angle of elevation
	which minimises the possible damages to themselves (assuming the ground
	is level) - i.e. they aim so that the point on the descending trajectory
	that is nearest to them is as far away as possible. With that intention,
	they choose the angle of elevation that minimises the damage to themselves
	if the shell explodes at its maximum height. What angle do they choose? 

	Does the shell then get any nearer to the gunners during its descent?