A kayak took 5 hours to finish its trip on a river. If it traveled at an
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There are two conditions necessary for total internal reflection, which is when light hits the boundary between two mediums and reflects back into its original medium:
Light is about to pass from a more optically dense medium (slower) to a less optically dense medium (faster).
The angle of incidence is greater than the defined critical angle for the two mediums, which is given by:
θ = sin⁻¹(/
)
Where θ = critical angle, = refractive index of faster medium,
= refractive index of slower medium.
Choice C gives one of the above necessary conditions.
Answer:
a) t = 11.2 s
b) v = 70.5 mph
Explanation:
a)
- Since we need to find the time, we could use the definition of acceleration (rearranging terms) as follows:
- where vf = 50 mph, and v₀ = 10 mph.
- However, we still lack the value of a.
- Assuming that the acceleration is constant, we can use the following kinematic equation:
- Since we know that Δx = 500 ft, we could solve (2) for a.
- In order to simplify things, let's first to convert v₀ and vf from mph to m/s, as follows:
- We can do the same process with Δx, from ft to m, as follows:
- Replacing (3), (4), and (5) in (2) and solving for a, we get:
- Replacing (6) in (1) we finally get the value of the time t:
b)
- Since the acceleration is constant, as we know the displacement is another 500 ft (152.4m), if we replace in (2) v₀ by the vf we got in a), we can find the new value of vf, as follows:
- If we convert vf again to mph, we have: