How to find initial velocity in projectile motion problems when you are not given the vlocity?

Suppose two stars are located in region a of the h-r diagram shown in the figure below. Star X appears much dimmer that Star Y as seen from Earth. Which Star can be inferred to be nearer to Earth, and how do you know?

You are driving at 90 km/h. How many meters are you covering per second?

Which is not true of atoms

A rotating merry-go-round and a rocket undergoing uniform acceleration both constitute their own inertial reference frame.

For each of the following news stories, determine whether the objects speed or velocity is given: the world record for the hundred-meters dash is about 10m/s; the wind today is 30 km/h from the north-west;

I can't figure this out, I could use an explanation too! A speeding truck travels in the positive x direction. It hits a car traveling in the positive y direction. The vehicles are deformed and travel together at an angle θ with the positive x-axis.

Based on your knowledge of the electromagnetic spectrum, why are radio waves considered harmless while ultraviolet waves and x-rays considered harmful?

What is great summary in physical science?

Does ice melt faster in water or air

Why are stars changing colurs by blinking?