Traditional Culture Encyclopedia - Photography and portraiture - Liaoning Chaoyang cos photography

Liaoning Chaoyang cos photography

(1) For people and seats, the resultant force of rope tension and gravity points to the center of the circle, which is determined by Newton's second law.

F=mgcosθ=60× 100.8N=750N

mgtanθ=mω2R

From the geometric relationship: r = r+lsinθ = 4+10× 0.6m =10m.

So the angular velocity ω = gtan θ r = 10× 34 10 radians/second = 32 radians/second.

(2) In the process of the turntable from standstill to steady speed, we can draw the following conclusions from the kinetic energy theorem:

W+(? mgh)= 12mv2? 0

h = l( 1-cosθ)= 10×( 1-0.8)m = 2m

v=ωR=32× 10m/s=53m/s

w = 12 mv2+mgh = 12×60×(53)2+60× 10×2j = 3450? J

(3) When the seat is stationary and rotates stably with the turntable, the electric energy consumed by the motor is E..

E×80%×80% = Northwest

Solution: e =10× 34500.80× 0.80j ≈ 5.4×104j.

Answer: When (1) is stable, the tension f of the wire rope on the seat is 750N, and the angular velocity ω of the turntable is 32 rad/s;

(2) The work done by the rope tension on the seat is 3450J during the period from the rest of each seat to the stable rotation of the turntable;

(3) If the efficiency of the motor driving the turntable is 80% and the mechanical power generated by the turntable rotating by itself and overcoming various friction losses is 20%, it is estimated that the electric energy consumed by the motor is 5.4× 104J. J moves from the seat to the stable rotation of the turntable.