```
import numpy as np
import matplotlib.pyplot as plt

t_max = float(input("Enter the maximum time (s): "))

a = 2 
v0 = 0 
x0 = 0 

t = np.linspace(0, t_max, 100)

v = v0 + a*t
x = x0 + v0*t + 0.5*a*t**2

plt.figure(figsize=(10, 4))

plt.subplot(1, 2, 1)
plt.plot(t, v)
plt.xlabel('Time (s)')
plt.ylabel('Velocity (m/s)')
plt.title('Velocity vs. Time')
plt.grid(True)

plt.subplot(1, 2, 2)
plt.plot(t, x)
plt.xlabel('Time (s)')
plt.ylabel('Position (m)')
plt.title('Position vs. Time')
plt.grid(True)

plt.tight_layout()
plt.show()
```
The provided code is already functional and will plot the velocity and position of an object under constant acceleration. However, to make it fully functional, we need to ensure that the user input is handled correctly. Here's the complete code:
Python
import numpy as np
import matplotlib.pyplot as plt

# Get maximum time from user input
t_max = float(input("Enter the maximum time (s): "))

# Define constants
a = 2  # acceleration in m/s^2
v0 = 0  # initial velocity in m/s
x0 = 0  # initial position in m

# Create time array
t = np.linspace(0, t_max, 100)

# Calculate velocity and position
v = v0 + a * t
x = x0 + v0 * t + 0.5 * a * t**2

# Plotting
plt.figure(figsize=(10, 4))

# Velocity vs Time
plt.subplot(1, 2, 1)
plt.plot(t, v)
plt.xlabel('Time (s)')
plt.ylabel('Velocity (m/s)')
plt.title('Velocity vs. Time')
plt.grid(True)

# Position vs Time
plt.subplot(1, 2, 2)
plt.plot(t, x)
plt.xlabel('Time (s)')
plt.ylabel('Position (m)')
plt.title('Position vs. Time')
plt.grid(True)

# Adjust layout and show plot
plt.tight_layout()
plt.show()
Matplotlib is building the font cache; this may take a moment.
This code will prompt the user for the maximum time and then display the corresponding velocity and position graphs.