Answer:
dα/dt = - 0,25 rad/sec
Step-by-step explanation:
The vertical wall, the ground from the vertical wall up to the ladder, and the ladder shape a right triangle. angle α will be the angle between the ladder and the ground, then:
cos α = distance between the wall and the down end of the ladder (x) / length of the ladder
cos α = x/ L
- sin α * dα/dt = dx/dt * L /L²
- sin α * dα/dt = dx/dt /L
When the down end of the ladder is 8 ft apart from the wall
cos α = 8 / 10 = 0,8 then cos² α + sin²α = 1
sin² α = 1 - cos²α sin²α = 1 - (0.8)² sin²α = 0.36
sin α = 0.6
dα/dt = ?
dx/ dt = 3/2
L = 10 ft
x = 8 ft
By substitution
- 0.6*dα / dt = (3/2) / 10
dα/dt = - 1.5 / 6
dα/dt = - 0,25 rad/sec
(-) means the angle is decreasing
