Two identical trains are moving on rails along the equator on the earth in opposite directions with the same speed. They will exert the same pressure on the rails.
Answer: False
Or read the worked solution below. Jump to the steps ↓
Written solution
Step 1: Define the parameters of the system.
Let the two identical trains each have mass , and let them move with speed relative to the Earth's surface along the equator in opposite directions.
Step 2: Determine the inertial speeds of the trains.
The Earth rotates about its axis with angular speed . In an inertial reference frame, the speed of the Earth's surface at the equator is , where is the radius of the Earth.
The inertial speed of the train moving in the direction of the Earth's rotation is:
The inertial speed of the train moving against the direction of the Earth's rotation is:
Step 3: Set up the equation of motion in the radial direction.
In the inertial frame, the net inward radial force provides the necessary centripetal acceleration for circular motion of radius .
Here, is the acceleration due to gravity, is the normal force exerted by the rails on the train, and is the inertial speed of the train.
Step 4: Calculate the normal force for each train.
Solve for the normal force , which is equal in magnitude to the force (and thus pressure) the train exerts on the rails.
For the train moving with the rotation:
For the train moving against the rotation:
Step 5: Compare the normal forces.
Find the difference between the two normal forces.
Since , the train moving against the Earth's rotation exerts a greater force on the rails than the train moving with the rotation.
Answer: The statement is FALSE. The train moving against the Earth's rotation exerts a greater pressure on the rails than the train moving with the rotation, with a difference in normal force of .