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Ph 211 – Challenge Problems (CP4) Name: ____________________

January 29, 2013

Due: February 5, 2013

Show your work clearly and completely for each of the following problems. Please answer the problems on separate papers or on the bottom of the page and on the back.

1. An enemy ship is on the east side of a mountain island, as shown. The enemy ship has maneuvered to within 2500m of the 1800 m high mountain peak and can shoot projectiles with an initial speed of 250 m/s. If the western shoreline is 300 m from the peak, what are the distances from western shore at which a ship can be safe from the bombardment of the enemy ship?

[pic]

2. A helicopter is flying horizontally above ground. At t = 0, from a certain height, the pilot drops a small motorized missile which can accelerate itself only horizontally. Eric has turned on the gravity, but due to air drag being present, the acceleration of gravity is smaller than 9.8 m/s2. The trajectory (y versus x) of the missile is shown below; the data points are in equal time intervals of 0.50 second.

a. Use the data points to determine y(t), and x(t). (you may use excel or graphical calculator for trend lines and regression)

b. Determine the acceleration of the missile (ax) and that of gravity (ay).

c. How fast was the helicopter moving when it dropped the missile?

t (sec) |0 |0.5 |1.0 | | | | | | | |x (m) |0 |10 | | | | | | | | |y (m) |80 |78 | | | | | | | | |

3. An object moves in the xy plane with constant acceleration. At t = 0 the object is at [pic] with velocity [pic]. At t = 3 s its velocity has changed to [pic] and has moved to position [pic].

a. Find magnitude and direction of [pic].

b. What is the acceleration of the object?

c. What is the magnitude of the object’s displacement at t = 3 s?

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1800m

2500m 300m

Vi=250m/s

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