Q. A particle moves along the x-axis so that at time t≥0 its position is given by x(t)=−t2+8t−9. Determine the speed of the particle at t=5.Answer:
Find Velocity Function: To find the speed of the particle at t=5, we first need to find the velocity, which is the derivative of the position function x(t) with respect to time t. The position function is x(t)=−t2+8t−9. We will calculate the derivative of x(t) to get the velocity function v(t).
Calculate Derivative: The derivative of x(t) with respect to t is v(t)=dtdx.Using the power rule, the derivative of −t2 is −2t, the derivative of 8t is 8, and the derivative of a constant (−9) is 0.So, v(t)=−2t+8.
Evaluate at t=5: Now we need to evaluate the velocity function v(t) at t=5 to find the speed at that specific time.Substitute t=5 into v(t) to get v(5)=−2(5)+8.
Calculate Speed: Calculate v(5) by performing the arithmetic operations.v(5)=−2(5)+8=−10+8=−2.
Final Result: The velocity of the particle at t=5 is −2 cm/s. However, speed is the absolute value of velocity, as it does not have a direction.Therefore, the speed of the particle at t=5 is ∣v(5)∣=∣−2∣=2 cm/s.
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