Q.

-A motor with a propeller (a push propeller) is attached to one end of a 30cm long carbon rod. The other end has a small weight equivalent to the motors weight.

-The entire system is hanged from a thread attached to a wall.. Now the motor is switched on.

-The motor provides thrust and the entire system rotates(in anticlockwise direction) about the center of the carbon rod. Now what will happen to the direction of the motor which is rotating (the direction in which the motor provides thrust) ??

a.) it will turn upwards facing the wall

b.) it will turn downwards gacing the ground

c.) no change in direction.. it will remain horizontal.

PLZ HELP.. I CUDNT SOLVE THIS FOR 5 DAYS :(

To tackle this question, we need to analyze the forces and torques acting on the system when the motor is turned on. The setup consists of a carbon rod with a motor and propeller on one end and a weight on the other. When the motor provides thrust, it creates a force that affects the entire system's orientation. Let's break it down step by step.

Understanding the Forces at Play

When the motor is activated, it generates thrust in a specific direction, which in this case is directed away from the motor. This thrust creates a torque about the center of the carbon rod, causing the system to rotate.

Analyzing the Rotation

The thrust from the motor acts horizontally, pushing the propeller away from the wall. As the system rotates anticlockwise around the center of the carbon rod, we need to consider how this rotation affects the orientation of the motor.

• Thrust Direction: The thrust is directed away from the motor, which means it initially pushes horizontally.
• Torque Effect: The torque generated by the thrust causes the entire system to rotate around the center of the rod.

What Happens to the Motor's Orientation?

As the system rotates anticlockwise, the motor will begin to change its orientation. Initially, if the motor is horizontal, as the system rotates, the thrust will cause the motor to tilt upwards. This is because the thrust vector will remain directed away from the motor, and as the rod rotates, the motor's position relative to the thrust direction will change.

Final Direction of the Motor

Given that the system rotates anticlockwise, the motor will eventually face upwards as it continues to rotate. Therefore, the correct answer to your question is:

• a.) it will turn upwards facing the wall

Visualizing the Scenario

Imagine holding a stick horizontally with a fan on one end. If you turn the stick anticlockwise, the fan will start to point upwards as it rotates. This analogy helps visualize how the thrust from the motor affects its orientation as the entire system rotates.

In summary, the thrust generated by the motor causes the system to rotate, and as it does, the motor will tilt upwards, facing the wall. This understanding of forces and motion is crucial in physics, especially when dealing with rotational dynamics.