1. A ball is thrown horizontally from the roof of a building 7.1 m tall and land

Question

1. A ball is thrown horizontally from the roof of a building 7.1m tall and lands 9.9m from the base.

A.) What was the ball's initial speed?

2. You are given a vector in the xy plane that has a magnitude of 84.0 units and a y component of-55.0 units.

A.)What are the two possibilities for its x component?

B.) Assuming the x component is known to be positive, specify the magnitude of the vector which, if you add it to the original one, would give a resultant vector that is 80.0 units long and points entirely in the ?x direction.

C.)Specify the direction of the vector.

Explanation / Answer

1) t = sqrt(2*7.1/9.8) = 1.203s

u = 9.9/1.203 = 8.229m/s

2) x^2 + 55^2 = 84^2

x = 63.49 and -63.49

B) So 63.49i-55j is the original vector

vector to be added = -80-63.49i+55j = -143.69i + 55j

C) Direction = 180 - tan^-1(55/143.69) = 159.05 degrees from positive x-axis

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