Math Problem Statement

A motorcycle is following a car that is traveling at constant speed on a straight highway. Initially, the car and the motorcycle are both traveling at the same speed of 22.5 m/sm/s , and the distance between them is 94.0 mm . After t1t1 = 4.00 ss , the motorcycle starts to accelerate at a rate of 5.00 m/s2m/s2 . The motorcycle catches up with the car at some time t2t2.How long does it take from the moment when the motorcycle starts to accelerate until it catches up with the car? In other words, find t2−t1t2−t1.

Express the time numerically in seconds using three significant figures.

**View Available Hint(s)**for Part B

Hint 1for Part B**.** Using a moving reference frame

Hint 2for Part B**.** Find the initial conditions for the position of the car

If the initial conditions are known at time t1t1, and the motion is one of constant acceleration, the equation for the position of the car at time t2t2 is

xc(t2)=x1,c+v1,c(t2−t1)+12ac(t2−t1)2xc(t2)=x1,c+v1,c(t2−t1)+12ac(t2−t1)2,

where xc(t)xc(t) is the positon of the car as a function of time, x1,cx1,c is its position at time t1t1, v1,cv1,cis the car's velocity at time t1t1, and acac is the car's constant acceleration. (If t1=0t1=0 , the equations become more familiar.) Let us choose a frame of reference in which at time t1t1, the motorcycle is at position x1,m=0x1,m=0. What are the values of x1,cx1,c, v1,cv1,c, and acac that you should use in the above equation?

Enter your answer in the order x1,c,v1,c,acx1,c,v1,c,ac, separated by commas as shown, in units of metersmeters, m/sm/s, and m/s2m/s2, respectively.

x1,c,v1,c,acx1,c,v1,c,ac =

94.0,22.5,0

mm, m/s,m/s, m/s2m/s2

SubmitPrevious Answers

 Correct

Important: If you use this answer in later parts, use the full unrounded value in your calculations.

Hint 3for Part B**.** Find the initial conditions for the position of the motorcycle

If initial conditions are known at time t1t1, and the motion is one of constant acceleration, the equation for the position of the motorcycle at time t2t2 is

xm(t2)=v1,m(t2−t1)+12am(t2−t1)2xm(t2)=v1,m(t2−t1)+12am(t2−t1)2,

where the meaning of the symbols is analogous to that of Part B.2. Observe that there is no term involving the initial position, because here we have assumed that at time t1t1, the motorcycle is at position x1,m=0x1,m=0. What are the values of v1,mv1,m and amam that you should use in the above equation?

Enter your answer in the order v1,m,amv1,m,am, separated by commas as shown, in units of m/sm/s and m/s2m/s2 respectively.

v1,m,amv1,m,am =

22.5,5.00

m/sm/s, m/s2m/s2

SubmitPrevious Answers

 Correct

Important: If you use this answer in later parts, use the full unrounded value in your calculations.

Hint 4for Part B**.** Solving for the time

At time t2t2, the car and motorcycle must be at the same position, since they are side by side. This means that you can set xc(t2)xc(t2) and xm(t2)xm(t2), the positions of the car and motorcycle at time t2t2, equal to each other, and then solve for the quantity t2−t1t2−t1. You should find that some terms cancel out on either side of the equation, which will make your calculations simpler.

Solution

To solve this problem, we will use the hints provided and set up the equations for the positions of both the car and the motorcycle. Then, we'll solve for the time it takes for the motorcycle to catch up with the car.

Step-by-Step Solution

1. Set Up the Equations of Motion

  • Car's Position Equation: The car is traveling at a constant speed, so its position xc(t)x_c(t) at time tt after t1=4.00st_1 = 4.00 \, \text{s} can be described by:

xc(t)=x1,c+v1,c(tt1)+12ac(tt1)2x_c(t) = x_{1,c} + v_{1,c} (t - t_1) + \frac{1}{2} a_c (t - t_1)^2

Given that x1,c=94.0mx_{1,c} = 94.0 \, \text{m} (the initial position of the car relative to the motorcycle), v1,c=22.5m/sv_{1,c} = 22.5 \, \text{m/s}, and ac=0m/s2a_c = 0 \, \text{m/s}^2 (since the car is moving at a constant speed), the equation simplifies to:

xc(t)=94.0+22.5(t4.00)x_c(t) = 94.0 + 22.5 (t - 4.00)

  • Motorcycle's Position Equation: The motorcycle starts accelerating at t1=4.00st_1 = 4.00 \, \text{s}, so its position xm(t)x_m(t) at time tt1t \geq t_1 is:

xm(t)=x1,m+v1,m(tt1)+12am(tt1)2x_m(t) = x_{1,m} + v_{1,m} (t - t_1) + \frac{1}{2} a_m (t - t_1)^2

Here, x1,m=0x_{1,m} = 0 (as we set the initial position of the motorcycle to be zero), v1,m=22.5m/sv_{1,m} = 22.5 \, \text{m/s}, and am=5.00m/s2a_m = 5.00 \, \text{m/s}^2. Thus, the equation becomes:

xm(t)=0+22.5(t4.00)+125.00(t4.00)2x_m(t) = 0 + 22.5 (t - 4.00) + \frac{1}{2} \cdot 5.00 (t - 4.00)^2

Simplifying, we have:

xm(t)=22.5(t4.00)+2.5(t4.00)2x_m(t) = 22.5 (t - 4.00) + 2.5 (t - 4.00)^2

2. Set the Positions Equal to Each Other to Find t2t1t_2 - t_1

At the time t=t2t = t_2, the motorcycle catches up with the car, meaning xc(t2)=xm(t2)x_c(t_2) = x_m(t_2). Therefore, we set the two equations equal to each other:

94.0+22.5(t4.00)=22.5(t4.00)+2.5(t4.00)294.0 + 22.5 (t - 4.00) = 22.5 (t - 4.00) + 2.5 (t - 4.00)^2

Simplifying, we can cancel the linear terms 22.5(t4.00)22.5 (t - 4.00) on both sides:

94.0=2.5(t4.00)294.0 = 2.5 (t - 4.00)^2

3. Solve for t2t1t_2 - t_1

Now solve for (t4.00)(t - 4.00):

(t4.00)2=94.02.5(t - 4.00)^2 = \frac{94.0}{2.5}

(t4.00)2=37.6(t - 4.00)^2 = 37.6

Take the square root of both sides:

t4.00=37.6t - 4.00 = \sqrt{37.6}

t4.006.13t - 4.00 \approx 6.13

Thus:

t2t1=t4.00=6.13st_2 - t_1 = t - 4.00 = 6.13 \, \text{s}

Final Answer

The time t2t1t_2 - t_1 it takes from the moment the motorcycle starts to accelerate until it catches up with the car is 6.13 seconds (to three significant figures).

Would you like more details or have any questions?

Here are 5 related questions to consider:

  1. What if the initial distance between the car and motorcycle was different? How would that affect t2t1t_2 - t_1?
  2. How would the result change if the motorcycle had a different acceleration?
  3. How far does the motorcycle travel while catching up to the car?
  4. What would happen if the car also started accelerating after t1t_1?
  5. Can you calculate the relative speed of the motorcycle as it catches up with the car?

Tip: When working with relative motion problems, remember to define a consistent frame of reference and account for initial conditions accurately.

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Math Problem Analysis

Mathematical Concepts

Kinematics
Constant acceleration equations
Relative motion

Formulas

Position equation under constant acceleration

Theorems

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Suitable Grade Level

Grades 11-12