Final answer:
When pushing the left pedal in a helicopter, it will turn counterclockwise around the yaw axis because of the increased thrust from the tail rotor that causes this directional change. The upward air pressure and the force from the helicopter blades are considered external forces affecting the helicopter's motion. Conventionally, the positive directions in coordinate systems are forward and to the right.
Step-by-step explanation:
When pushing the left pedal in a helicopter, the helicopter will turn counterclockwise around the yaw axis. This is due to Newton's third law of action and reaction, as well as the principles of helicopter dynamics. The left pedal actuates the tail rotor to change its pitch and create more thrust in the opposite direction, causing the helicopter's nose to rotate to the left, leading to a counterclockwise motion.
The air pushing upward on the helicopter can be considered an external force, as it comes from outside the helicopter system. It affects the helicopter's motion by providing lift. Similarly, the downward force applied by the helicopter blades is also an external force in relation to the body of the helicopter, as these blades are acting on the air, which in turn generates lift.
Check Your Understanding: In conventional coordinate systems used for motion, the directions considered positive are forward and to the right.