1. A projectile is fired from ground level at an angle above the horizontal on an airless planet where g = 10.0 m/s2. The initial x and y components of its velocity are 86.6 m/s and 50.0 m/s respectively. How long after firing does it take before the projectile hits the level ground?
A. 5.00 seconds
B. 10.00 seconds
C.15.00 seconds
D. 20.00 seconds
2. A rock is thrown from the roof of a building, with an initial velocity of 10 m/s at an angle of 30o above the horizontal. The rock is observed to strike the ground 43 m from the base of the building. What is the height of the building assuming no air resistance?
3. A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30, and the coefficient of kinetic friction is 0.20. What horizontal force must be applied to the box to cause it to start sliding along the surface?
(Please Show Work/Explain)