Nice to see you again.
( 1)
The diameter of the wheel is 40 cm, and the circumference of one revolution is 40 cm× 3.1416 =125.664 cm.
The length of the steel wire is 50.24 meters, which is 5024 centimeters.
The wheel of a unicycle should turn 5024÷ 125.664=39.98≈40 times, and it can ride a steel wire of 50.24 meters.
(2)
Draw a circle with the effective range of heavy machine guns 1500m as the radius, and the area of this circle is:
( 1500m ÷2)？ ×3. 14 16 = 562500 m2×3. 14 16 = 1767 150 m2。
The shooting angle of 70 is 70/360 of the whole circle area.
So the area controlled by machine guns is 1767 150 m2× 70/360 = 34312.5 m2.
Don't you think so? Good luck. Goodbye.