An object moves in a straight line. It starts from the rest and its acceleration is \(2 \mathrm{~ms}^{-2}\). After reaching a certain point it comes back to the original point. In this movement its acceleration is $-3 \mathrm{~ms}^{-2}$. till it comes to rest. The total time taken for the movement is 5 second. Calculate the maximum velocity. (A) \(6 \mathrm{~ms}^{-1}\) (B) \(5 \mathrm{~ms}^{-1}\) (C) \(10 \mathrm{~ms}^{-1}\) (D) \(4 \mathrm{~ms}^{-1}\)

Short Answer

Expert verified
The maximum velocity is \(6 \mathrm{~ms}^{-1}\) (A).

Step by step solution

01

Write equations for displacement for each part of motion

Since the object comes back to the original position, the displacement in each part of the motion must be equal and opposite. Using the equation: \(x = ut + \frac{1}{2}at^2\), we have: For the first part of the motion: \(x = 0 + \frac{1}{2}(2)t_1^2\) For the second part of the motion: \(-x = 0 + \frac{1}{2}(-3)t_2^2\)
02

Solve for the time taken in each part of the motion

Using the given information t1 + t2 = 5 s, and equating the magnitudes of displacement from the previous step, we have: \(t_1^2 = \frac{3}{2}t_2^2\) Substituting t2 = 5 - t1, we get: \(t_1^2 = \frac{3}{2}(5 - t_1)^2\) Solve for t1: \(t_1 \approx 3 \mathrm{s}\) So, t2 = 5 - t1 = 2 s.
03

Find maximum velocity

Now we know the time taken for the first part of the motion, we can calculate the maximum velocity using the initial velocity and acceleration for that part: \(v_\text{max} = u_1 + a_1t_1\) Since the object starts from rest, u1 = 0. The acceleration for the first part of the motion, a1 = 2 ms^-2, and the time taken, t1 = 3 s. Thus, we can plug in these values to find the maximum velocity: \(v_\text{max} = 0 + (2)(3)\) \(v_\text{max} = 6 \mathrm{~ms}^{-1}\) Therefore, the maximum velocity is \(6 \mathrm{~ms}^{-1}\) and the correct answer is (A) \(6 \mathrm{~ms}^{-1}\).

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