Distance from the head shadow to the projection point of the lamp on the ground: lamp height = straight line distance from the person to the lamp perpendicular to the ground: lamp height to the person.

x : H = L : (H-h)

We have a speed of v people = d L/dt, and the head shadow speed v shadow = d x/dt.

Therefore, V shadow = v people * [H/(H-h )]

8、

VX(t)= VX(0)+ integer ax(t) dt = 0-3 sin(t) = -3 sin(t)

vy(t) = 4 + 4 cos(t) - 4 cos(0) = 4 cos(t)

X(t)= x0+ integral (VX (t) dt) = 3+3cos (t)-3cos (0) = 3cos (t).

y(t) = 0 + 4 sin(t)

There is the formula sin (x) 2+cos (x) 2 = 1.

We have [x (t [x (t)/3] 2+[y (t)/4] 2 =1+0.

9、s = 2π* R

S = integral (a+b t) dt = a t+b t 2/2.

Tangential acceleration b

Normal acceleration (a+b t) 2/r = [(a 2+2 a b t+b b b t 2)/r]

= [(A^2+2 b seconds)/R]

= a^2/r+4 bπ