Reference Frames And Relative Motion
A train moves east at 15 m/s relative to the ground. A passenger walks east at 2.0 m/s relative to the train. Determine the velocity of the passenger relative to the ground.
A cyclist travels west at 12 m/s relative to the ground. A car travels west at 20 m/s relative to the ground. Determine the velocity of the car relative to the cyclist.
An observer stands on a riverbank. A boat moves north at 6.0 m/s relative to the water, and the river current flows north at 2.0 m/s relative to the ground. What velocity does the riverbank observer measure for the boat?
A ball accelerates at 5.0 m/s² as measured by a passenger inside a bus moving at constant velocity. Which statement correctly describes the acceleration measured by a ground observer?
A helicopter flies east at 40 m/s relative to the ground. A wind blows west at 15 m/s relative to the ground. Determine the velocity of the helicopter relative to the air.
A student claims that “velocity is always the same no matter who observes it.” Identify the error in this claim and state one quantity that is the same for all inertial observers.
A person walks at 1.5 m/s toward the back of a train that moves east at 22 m/s relative to the ground. Determine the velocity of the person relative to the ground.
Two runners sprint along a straight track. Runner A moves north at 8.0 m/s relative to the ground, and Runner B moves south at 6.0 m/s relative to the ground. Determine the velocity of Runner A relative to Runner B.
A drone flies west at 10 m/s relative to the air. The air moves east at 10 m/s relative to the ground. What does a ground observer measure as the drone’s velocity?
During a physics demonstration, a student sits on a cart rolling east at constant velocity and tosses a ball straight up. The student observes the ball go up and come back down into their hand. Which description of the ball’s path is correct for a ground observer?
A ship sails south at 8.0 m/s relative to the ocean current. The current flows north at 3.0 m/s relative to the ground. A lighthouse keeper on shore measures the ship’s velocity. Which value is correct?
Two inertial observers measure the velocity of the same falling ball. Observer P is stationary on the ground. Observer Q rides in an elevator moving upward at constant velocity. Which row correctly compares their measurements?
A rescue boat must reach a swimmer located directly upstream. The river flows south at 4.0 m/s relative to the ground. The boat can travel at 7.0 m/s relative to the water. If the boat heads directly north through the water, calculate its velocity relative to the ground.
A freight train moves east at 16 m/s relative to the ground. A second freight train moves east at 10 m/s relative to the ground on a parallel track. A worker on the second train throws a tool east at 3.0 m/s relative to their train. Determine the velocity of the tool relative to the first train.
An engineer on a stationary platform watches two cars approach each other on a straight road. Car X moves east at 25 m/s and Car Y moves west at 30 m/s, both relative to the ground. The engineer claims the cars close the gap between them at 55 m/s. A passenger in Car X claims the gap closes at 55 m/s as well. Which statement best explains this agreement?