Final answer:
Calculating the time for an asteroid traveling at 20 km/s to cover a distance of 4.0 x 10⁶ km, we find the impact would occur after approximately 5555.56 hours if a mission to change its course fails.
Step-by-step explanation:
The question is a physics problem involving the motion of an asteroid toward Earth and considers what would happen if a mission to alter the asteroid's trajectory fails.
To find out how many hours until the asteroid impacts Earth, we need to calculate the time taken for an asteroid traveling at a constant speed to cover a given distance. The asteroid is moving at 20 km/s, and it is 4.0 x 10⁶ km away from Earth. We can use the formula Δt = d/v, where Δt is the time, d is the distance, and v is the velocity.
The calculation is as follows:
Convert the distance from kilometers to meters: 4.0 x 10⁶ km * 10³ m/km = 4.0 x 10⁹ m.
Calculate the time in seconds: Δt = 4.0 x 10⁹ m / (20 x 10³ m/s) = 2.0 x 10⁵ s.
Convert the time from seconds to hours: 2.0 x 10⁵ s / (3600 s/hr) ≈ 5555.56 hours.
Therefore, if the mission fails, the asteroid would impact Earth after approximately 5555.56 hours.