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Displacement via Net Change Theorem

An object moves along a straight line with velocity v(t)=1t+1v(t) = \dfrac{1}{t+1} meters per second, for t≥0t \geq 0 measured in seconds.

Use the Net Change Theorem to find the displacement of the object on the interval [0,10][0, 10]. That is, compute ∫0101t+1 dt.\int_0^{10} \frac{1}{t+1}\,dt.

Hint

Let u=t+1u = t+1, so du=dtdu = dt. Rewrite the integral in terms of uu, update the bounds accordingly, and then evaluate using the antiderivative of 1/u1/u.

Step-by-step solution

Let u=t+1u = t+1, so du=dtdu = dt. When t=0t=0, u=1u=1, and when t=10t=10, u=11u=11. The integral becomes ∫1111u du.\int_1^{11} \frac{1}{u}\,du.

This evaluates to ln⁡∣u∣∣111=ln⁡(11)−ln⁡(1)=ln⁡(11)\ln|u|\Big|_1^{11} = \ln(11) - \ln(1) = \ln(11). Since velocity is positive throughout [0,10][0,10], this value also represents the total distance traveled, and the displacement is ln⁡(11)\ln(11) meters.

Sign of Velocity on the Interval

Hint
Step-by-step solution

They are equal. Since v(t) = 1/(t+1) is positive for all t in [0,10], the object never reverses direction, so the total distance traveled matches the net displacement exactly, both equal to ln(11) meters.

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