Consider the following problem:The air gap (the distance from the bottom of the bridge to the surface of the water) under a bridge is changing at a rate of r(t)=0.6sin(6πt) meters per hour (where t is the time in hours). At time t=13, the air gap is 62 meters. What is the air gap when t=15 hours?Which expression can we use to solve the problem?Choose 1 answer:(A) r′(13)+62(B) r′(15)(C) 62+∫1315r(t)dt(D) 62+∫1315r′(t)dt
Q. Consider the following problem:The air gap (the distance from the bottom of the bridge to the surface of the water) under a bridge is changing at a rate of r(t)=0.6sin(6πt) meters per hour (where t is the time in hours). At time t=13, the air gap is 62 meters. What is the air gap when t=15 hours?Which expression can we use to solve the problem?Choose 1 answer:(A) r′(13)+62(B) r′(15)(C) 62+∫1315r(t)dt(D) 62+∫1315r′(t)dt
Understand the Problem: Understand the problem.We are given the rate of change of the air gap as a function of time, r(t), and the air gap at a specific time, t=13 hours. We need to find the air gap at a later time, t=15 hours.
Determine Approach: Determine the correct approach to find the air gap at t=15 hours.Since we are given the rate of change of the air gap, we need to integrate this rate from t=13 to t=15 to find the total change in the air gap over this time period. Then we add this change to the air gap at t=13 to find the air gap at t=15.
Identify Expression: Identify the correct expression to use.The correct expression to use is the integral of the rate of change from t=13 to t=15, added to the air gap at t=13. This corresponds to option (C) 62+∫1315r(t)dt.
Calculate Integral: Calculate the integral of the rate of change from t=13 to t=15. We need to integrate r(t)=0.6sin(6πt) from t=13 to t=15. ∫1315r(t)dt=∫13150.6sin(6πt)dt Let's calculate this integral.
Perform Integration: Perform the integration.To integrate 0.6sin(6πt), we use the substitution method. Let u=6πt, then du=6πdt, and dt=π6du.The limits of integration change accordingly: when t=13, u=6π⋅13; when t=15, u=6π⋅15.Now we integrate with respect to u:∫0.6sin(u)⋅π6du from u=6π⋅13 to u=6π⋅15.
Calculate New Integral: Calculate the new integral with the substitution.The integral becomes:(0.6×π6)∫sin(u)du from u=6π×13 to u=6π×15.This simplifies to:(π3.6)×[−cos(u)] from u=6π×13 to u=6π×15.
Evaluate Integral: Evaluate the integral at the new limits.We substitute the limits into the antiderivative:(π3.6)∗[−cos(6π∗15)+cos(6π∗13)].
Simplify Expression: Simplify the expression and calculate the values.We calculate the cosine values and simplify the expression:(3.6/π)⋅[−cos((5π)/2)+cos((13π)/6)].Note that cos((5π)/2)=0 and cos((13π)/6) is equivalent to cos(π/6) due to periodicity of the cosine function.So, the expression simplifies to:(3.6/π)⋅[0+3/2].
Multiply by Coefficient: Multiply the result by the coefficient.(π3.6)×(23)=2π3.6×3.
Add to Air Gap: Add the result to the air gap at t=13 to find the air gap at t=15. The change in air gap from t=13 to t=15 is 2π3.6×3 meters. We add this to the air gap at t=13, which is 62 meters. Air gap at t=15 = 62+2π3.6×3.
Calculate Final Value: Calculate the final value.We calculate the numerical value of the expression:Air gap at t=15=62+2π(3.6×3)≈62+(2×3.14159)(3.6×1.732)≈62+(6.28318)(6.2352)≈62+0.992≈62.992 meters.
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