The Kingda Ka roller coaster at Six Flags Great
Adventure is higher than the Statue of Liberty at
456 feet tall. If the total mass of the carts is 550
kg and is treated as a point mass. With what
speed would the cart be traveling at when it
reaches the bottom of the roller coaster if the
cart originally had a speed of 5 m/s at the top of
the roller coaster?



Answer :

Let's solve this step-by-step:

1. Convert Height from Feet to Meters:
- The height of the Kingda Ka coaster is 456 feet.
- Convert this height into meters. We know that 1 foot equals 0.3048 meters.
[tex]\[ \text{Height in meters} = 456 \text{ feet} \times 0.3048 \text{ meters/foot} = 138.9888 \text{ meters} \][/tex]

2. Calculate the Potential Energy at the Top of the Coaster:
- The potential energy (PE) at the top is given by the formula [tex]\(PE = m \cdot g \cdot h\)[/tex], where:
- [tex]\(m\)[/tex] is the mass of the carts (550 kg),
- [tex]\(g\)[/tex] is the acceleration due to gravity (9.81 m/s²),
- [tex]\(h\)[/tex] is the height in meters (138.9888 meters).
[tex]\[ PE_{\text{top}} = 550 \text{ kg} \times 9.81 \text{ m/s}^2 \times 138.9888 \text{ meters} = 749914.0704 \text{ Joules} \][/tex]

3. Calculate the Kinetic Energy at the Top of the Coaster:
- The kinetic energy (KE) at the top is given by the formula [tex]\(KE = \frac{1}{2} m v^2\)[/tex], where:
- [tex]\(m\)[/tex] is the mass of the carts (550 kg),
- [tex]\(v\)[/tex] is the initial speed (5 m/s).
[tex]\[ KE_{\text{top}} = \frac{1}{2} \times 550 \text{ kg} \times (5 \text{ m/s})^2 = 6875 \text{ Joules} \][/tex]

4. Total Mechanical Energy at the Top of the Coaster:
- The total energy at the top is the sum of the potential energy and kinetic energy.
[tex]\[ E_{\text{top}} = PE_{\text{top}} + KE_{\text{top}} = 749914.0704 \text{ Joules} + 6875 \text{ Joules} = 756789.0704 \text{ Joules} \][/tex]

5. At the Bottom of the Coaster:
- When the cart reaches the bottom, the height is 0, hence the potential energy (PE) at the bottom is 0.
- Since energy is conserved, the total mechanical energy at the bottom will be equal to the total mechanical energy at the top, which is [tex]\(756789.0704\)[/tex] Joules.
- Thus, all of the potential energy at the top will convert into kinetic energy at the bottom.

6. Calculate the Final Speed at the Bottom:
- The kinetic energy at the bottom is equal to the total mechanical energy (since potential energy at the bottom is 0):
[tex]\[ KE_{\text{bottom}} = E_{\text{top}} = 756789.0704 \text{ Joules} \][/tex]
- Use the kinetic energy formula [tex]\(KE = \frac{1}{2} m v^2\)[/tex] and solve for the final speed [tex]\(v\)[/tex]:
[tex]\[ 756789.0704 \text{ Joules} = \frac{1}{2} \times 550 \text{ kg} \times v^2 \][/tex]
- Rearranging to solve for [tex]\(v\)[/tex]:
[tex]\[ v^2 = \frac{2 \times 756789.0704 \text{ Joules}}{550 \text{ kg}} \approx 2749.23 \text{ m}^2/\text{s}^2 \][/tex]
[tex]\[ v = \sqrt{2749.23 \text{ m}^2/\text{s}^2} \approx 52.46 \text{ m/s} \][/tex]

Therefore, the speed of the cart when it reaches the bottom of the roller coaster is approximately 52.46 meters per second.