2. Twin sisters, Anna and Zelma, are twenty years old. Anna stays on the Earth while Zelma gets on a 20.0-meter-long spaceship that travels at constant speed 0.98c to a distant star. The star is 9.00 lightyears away as measured by Anna. Zelma immediately turns around and travels back to the Earth at the same speed of 0.98c. a) What length does Anna measure for the spaceship while it is moving? b) Upon Zelma's return, which twin is seen to be older now on Earth and what is the age difference?

9. An astronomer on earth observes two spacecraft moving away from each other along an axis that passes through the earth. The astronomer measures the speed of each spacecraft to be 0.875c relative to the earth. At what speed are the spacecrafts moving apart relative to each other? a) 0.496c b) 0.467c c) 1.750c d) 0.143c e) 0.991c 10. How far apart must two objects on the moon be to be resolved by a telescope which has a 7.80-m diameter mirror? The wavelength of the light used is A610 nm, and the distance to the moon to be 3.80 x 105 km. a) 24.4 m b) 29.7 m c) 36.3 m d) 72.5 m e) 12.2 m 11. A converging lens with a focal length of (f₁ = 32.0 cm) is placed 42.0 cm to the left of a diverging lens with a focal length of (f2 = -25.5 cm). An object is placed 40.0 cm to the left of the converging lens. What is the location of the image produced by the combination of lenses? a) 32.5 cm to the right of the diverging lens b) 32.5 cm to the left of the diverging lens c) 160 cm to the left of the…

2. A ladder 5.50 m long leans against a wall inside a spaceship. From the point of view of a person on the ship, the top of the ladder is 4.61 m above the floor. The spaceship moves past the Earth with a speed of 0.80c in a direction parallel to the floor of the ship. What is the length of the ladder as seen by an observer on Earth?