I have a test tomorrow can anyone please help me with these

I have a test tomorrow can anyone please help me with these two questions?1. Find the linear speed of a wheel that rotates at 9.1 turns in 4.1 seconds with a diameter of 52 cm. Also find the centripetal acceleration of the wheel. -The formula that I have for linear speed is Velocity = omega x Radius-The answer is Linear speed = 295.3 radians Centripetal acceleration = 215 newtons I am having trouble solving it. How do I do it?2. A 1143 kg roller coaster car goes through a loop with a radius of 15 meters. At what linear speed will the coaster have to obtain when inverted in the loop in order for it to safely make it without falling(assume the car is not attached to the rail)- Answer: 12.12m/sI am having trouble solving it. How do I do it?

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