76. A projectile is launched from ground level with an initial speed of 53 m/s. Find the launch angle (the angle the initial velocity vector is above the horizontal) such that the maximum height of the projectile is equal to its horizontal range. (Ignore any effects due to air resistance.)

74. A cannonball is fired with initial speed o at an angle 30

above the horizontal from a height of 40 m above the ground. The projectile strikes the ground with a speed of 1.20. Find o (Ignore any effects due to air resistance.)

22 (a) Which of the free-body diagrams in Figure 4-34 represents a block sliding down a frictionless inclined surface? (b) For the correct diagram, label the forces and tell which are contact forces and which are action-at-a-distance forces. (c) For each force in the correct diagram, identify the reaction force, the object it acts on and its direction. (a) (b) (c) (d)