Velocity imparted by twist.linear

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Hi, I am publishing twist.linear.x = 0.5 on cmd_vel topic within the callback function of /pose topic. Whenever pose in x direction of my bot is less than goal x component I publish the twist command. For the /pose callback I am using rosspin with a ros::rate of 0.5 hz (ie 1 time in 2 seconds). Does it mean that 0.5 m/s will be imparted to my bot until the next iteration of /pose callback continuously or it will impart 0.5 for an instant and my bot will be still and wait for next iteration? Thanks in advance!