Question

Marc is trying to break into Bill Gates’ house in the middle of the night to sabotage Windows (he is part of the Mac cult). He stands 14.0 m away from the 5 m tall fence that surrounds Bill’s estate. To test the security system, Marc wants to throw a rock over the fence to see if it will trigger any alarms. Being a physicist, Marc is zero upper body strength (actually he has zero strength anywhere in his body) and needs to use physics to help throw this rock over the fence. Marc notes that the ground is level on either side of the fence and uses the fact that he is 1.6 m tall. Given his build, he concludes that he will throw the rock at a 56 degree angle.

1. (a) What minimum initial speed must the rock have as it leaves Marc’s hand to clear the top of the fence?

2. (b) For the initial velocity calculated in part (a), what horizontal distance beyond the fence will the rock land on the ground? (don’t forget that full marks are only aware if there is a final derived equation. Since the formula for v0 is a bit cumbersome, your final derived equation may be in terms of v0.)

3. (c) If Marc was specifically aiming for a glass window, should he aim directly at his target? How should the launch angle depend on horizontal distance to the target?

Answer 1

c) If marc had to aim for the glass window , he should aim for slightly above the window, since due to gravity effect rock will fall a bit down.