Help with this Ferris wheel rotational physics problem please

In summary, the conversation discusses an attempted calculation involving mass, centripetal acceleration, and gravitational acceleration. However, the summary points out that there is a sign error in the calculation and the correct equation should be a2= -ac +9.8. This change makes downward acceleration positive and leads to a corrected value for the mass of 7.9 kg.
  • #1
takelight2
12
1
Homework Statement
A woman rides on a Ferris wheel of radius 16m that maintains the same speed throughout its motion. To better understand physics, she takes along a digital bathroom scale (with memory) and sits on it. When she gets off the ride, she uploads the scale readings to a computer and creates a graph of scale reading versus time. (Figure 1) Note that the graph has a minimum value of 510N and a maximum value of 666N. The acceleration due to gravity, g=9.80m/s2.
Relevant Equations
What is the woman's mass?

Express your answer in kilograms.
So this is what I've attempted:

666 = m*a1
510 = m*a2

a1= ac + 9.8
a2= ac-9.8

666 = m(ac+9.8)
510 = m(ac-9.8)

666 = m*ac + m*9.8
510 = m*ac - m*9.8

156 = 2m(9.8)

m = 7.9 kg (which seems very wrong haha)

any ideas?? I thought my reasoning was okay, since I considered that at the top of the wheel (where weight is max), both the centripetal acceleration and the gravitational acceleration point downward, and at the bottom (weight is min) they point in opposite directions so they must subtract.. What am I doing wrong here?
 
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  • #2
takelight2 said:
What am I doing wrong here?
You are making a sign error. The 510 N and 666 N are in the same direction as g
 
  • #3
BvU said:
You are making a sign error. The 510 N and 666 N are in the same direction as g

Oh ok. So then i can just change a2= -ac +9.8, making downward positive.

Ok thanks a lot.
 

1. What is the formula for calculating rotational motion in a Ferris wheel?

The formula for calculating rotational motion in a Ferris wheel is angular velocity (ω) = 2π / time period (T).

2. How do I determine the angular velocity of a Ferris wheel?

To determine the angular velocity of a Ferris wheel, you need to know the time period (T) of one complete revolution. Then, use the formula ω = 2π / T to calculate the angular velocity.

3. How does the radius of the Ferris wheel affect its rotational motion?

The radius of the Ferris wheel affects its rotational motion by changing the distance traveled by each point on the wheel in one revolution. A larger radius will result in a larger distance traveled and a higher angular velocity.

4. What is the difference between linear and angular velocity in a Ferris wheel?

Linear velocity refers to the speed at which a point on the Ferris wheel is moving along its circular path, while angular velocity refers to the rate of change of the angular displacement of the wheel. In simpler terms, linear velocity is the speed of the Ferris wheel, while angular velocity is the speed of rotation.

5. How does the mass of the Ferris wheel affect its rotational motion?

The mass of the Ferris wheel does not directly affect its rotational motion. However, a heavier wheel may require more energy to rotate and may have a slower angular velocity compared to a lighter wheel. The mass of the riders on the wheel can also affect its rotational motion, as it changes the overall mass of the system.

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