Q16 · 2023 · Paper 1Complex familiar1 mark
QUESTION 16
A train is travelling at relativistic speed and is about to move through a tunnel. An observer on the train measures the train and tunnel to each be 95 m long. A second observer is stationary relative to the tunnel. They would observe the train to
(A)
simultaneously enter and exit the tunnel.
(B)
decrease its mass while in the tunnel.
(C)
move faster while in the tunnel.
(D)
be shorter than the tunnel.
WORKED SOLUTION
1 markAnswer D
ANSWER
D
Worked solution
The tunnel is at rest for the stationary observer, while the moving train is length-contracted. The stationary observer therefore measures the train as shorter than the tunnel. Option D.
Selects option D.
Worked explanation by QCE Vault; correct option verified against the QCAA answer key.