A pulsar is a rapidly rotating neutron star that emits a radio beam the way a lighthouse emits a light beam. We receive a radio pulse for each rotation of the star. The period T of rotation is found by measuring the time between pulses. The pulsar in the Crab nebula has a period of rotation of T = 0.033 s that is increasing at the rate of 1.26 x 10 −5 s/y. (a) What is the pulsar's angular acceleration α? (b) If α is constant, how many years from now will the pulsar stop rotating? (c) The pulsar originated in a supernova explosion seen in the year 1054. Assuming constant α, find the initial T.
A pulsar is a rapidly rotating neutron star that emits a radio beam the way a lighthouse emits a light beam. We receive a radio pulse for each rotation of the star. The period T of rotation is found by measuring the time between pulses. The pulsar in the Crab nebula has a period of rotation of T = 0.033 s that is increasing at the rate of 1.26 x 10 −5 s/y. (a) What is the pulsar's angular acceleration α? (b) If α is constant, how many years from now will the pulsar stop rotating? (c) The pulsar originated in a supernova explosion seen in the year 1054. Assuming constant α, find the initial T.
A pulsar is a rapidly rotating neutron star that emits a radio beam the way a lighthouse emits a light beam. We receive a radio pulse for each rotation of the star. The period T of rotation is found by measuring the time between pulses. The pulsar in the Crab nebula has a period of rotation of T = 0.033 s that is increasing at the rate of 1.26 x 10−5 s/y. (a) What is the pulsar's angular accelerationα? (b) If α is constant, how many years from now will the pulsar stop rotating? (c) The pulsar originated in a supernova explosion seen in the year 1054. Assuming constant α, find the initial T.
Definition Definition Rate of change of angular velocity. Angular acceleration indicates how fast the angular velocity changes over time. It is a vector quantity and has both magnitude and direction. Magnitude is represented by the length of the vector and direction is represented by the right-hand thumb rule. An angular acceleration vector will be always perpendicular to the plane of rotation. Angular acceleration is generally denoted by the Greek letter α and its SI unit is rad/s 2 .
The gravitational force exerted by the planet Earth on a unit
mass at a distancer from the center of the planet is
GMr
if rR
where M is the mass of Earth, Ris its radius, and G is the
gravitational constant. Is F a continuous function of r?
In a certain binary-star system, each star has the a mass of 1.08 x 1030 kg, and they revolve about their center of mass. The distance between them is 1.9 × 108 km. What is their period of revolution in Earth
years?
X Y
Kepler's third law states that for any object in a gravitational orbit,
P2∝a3P2∝a3
where PP is the orbital period of the object and aa is the average distance between the object and what it is orbiting.
In our Solar System, the natural units are distances measured in astronomical units (A.U.) and orbital periods measured in years. This can be seen for the Earth-Sun system which has an orbital period P=1P=1 year and an average distance a=1a=1 AU. Using these natural units in the Solar System, the proportionality becomes an equality, so for our Solar System:
(Pyears)2=(aA.U.)3(Pyears)2=(aA.U.)3 .
Using your mathematical prowess, determine what the orbital period in years would be for an asteroid that was discovered orbiting the Sun with an average distance of 25 astronomical units.
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