Please help :)

Describe the structure of an alpha particle

1. most waves are caused by vibrations. what motion in a transmitting antenna causes the vibrations that produce radio waves? 2. name two common household appliances that produce electromagnetic waves other than radio waves. what kind of electromagnetic waves do they produce? 3. when you are in a car and it passes through a tunnel, the radio signal is sometimes lost. why do you think this happens?

Aplanet of mass m 6.75 x 1024 kg is orbiting in a circular path a star of mass m 2.75 x 1029 kg. the radius of the orbit is r 8.05 x107 km. what is the orbital period (in earth days) of the planet tplanet?

Assume you measured the mass of the cart to be (500 ± 1) g and the mass of the additional mass you put on the cart to be (500 ± 1) g as well. since the scale you are using in the lab cannot measure objects heavier than 600g you will have to sum up individual pieces and propagate the error. so what would be the mass and the standard error of the cart and the mass