Exam 39: Relativity

A spaceship moving past the Earth with a speed of 0.800 c signals to the Earth with pulsed laser photons emitted at 10.0-second intervals according to the spaceship's clock.According to observers on Earth who see the flashes,the time interval they measure is

A 1000-kg automobile moving with a speed of 24 m/s relative to the road collides with a 500-kg automobile initially at rest.If the two stick together,what is the velocity in m/s of the two cars after the collision according to an observer in a truck moving 10 m/s in the same direction as the moving cars?

Hanna,at rest in her spaceship which is moving past Earth at 0.800 c,observes a neutron at rest relative to her spaceship decay into a proton,an electron and a neutrino.She notes that the total momentum, ,of the decay products is zero after the decay.According to an observer on Earth,the magnitude of the total momentum of the decay products, ,is

A jet plane travels around the world at 2 000 mi/hr (894 m/s).Two accurate atomic clocks measure the times of flight,one on board the plane and the second on Earth.If it takes 12 hours to complete the journey,what will the time difference (in μs)be?

Boat 1 goes directly across a stream a distance L and back taking a time t₁.Boat 2 goes down stream a distance L and back taking a time t₂.If both boats had the same speed relative to the water,which of the following statements is true?

A spaceship from another galaxy passes over the solar system directly above a radial line from the sun to the Earth.(We measure that distance to be 1.5 × 10¹¹ m. )On Earth,the spaceship is observed to be traveling at a speed of 0.80 c,for which γ = 5/3.As measured on Earth it takes the spaceship 625 seconds to travel from the sun to Earth.When a scientist in the spaceship measures the Earth-sun distance and the time it takes her to travel that distance,she finds the results are respectively

The half-life of a muon is 2.2 μs.How fast is it moving relative to an observer who says its half-life is 4.4 μs?

A proton has a total energy of 2.5 × 10−¹⁰ J.How fast is it moving? (M = 1.67 × 10−²⁷ kg)

A 1000-kg automobile moving with a speed of 24 m/s collides with a 500-kg car initially at rest.If the two stick together,what is the velocity (in m/s)of the two cars after the collision relative to an automobile moving in the same direction at 15 m/s?

Fireworks go off at the same time according to Earth clocks in two cities,Alum and Boron,that are 300 km apart.The people in a spaceship that is flying in a straight line from Alum to Boron at 0.80 c also observe the fireworks.Do they see the fireworks in the two cities simultaneously? If the people in the spaceship say the fireworks were not simultaneous in Alum and Boron,how long before or after the fireworks flashed at Alum did the fireworks flash at Boron according to their calculations? (The spaceship is directly over Alum when the fireworks flash. )

A spaceship moves at a speed of 0.95 c away from the Earth.It shoots a star wars torpedo toward the Earth at a speed of 0.90 c relative to the ship.What is the velocity of the torpedo relative to the Earth? (The direction in which the spaceship moves is the positive direction. )

A 30-year-old woman takes a trip on a rocket,leaving her 20-year-old brother behind.She travels at a speed of 0.8 c,and is gone 20 years,according to the younger brother.When she returns,how many years older/younger is she than her brother?

In a classroom on the first spaceship to an extrasolar planet--there are children because the trip will take 200 years--a teacher is showing charge Q uniformly distributed along a conducting rod of length L₀ to produce linear charge density λ₀.As observed on Pluto when the spaceship passes it at 0.800 c,the linear charge density Is

When at rest,a spacecraft has the same height as length.When moving at relativistic speeds in the direction of its length,which one of the following describes its length and height to an observer at rest?