Particle moves in a circle of radius 90m with a constant speed 25m/s. how many revolution does it make in 30sec

Scientists use laser range-finding to measure the distance to the moon with great accuracy. a brief laser pulse is fired at the moon, then the time interval is measured until the "echo" is seen by a telescope. a laser beam spreads out as it travels because it diffracts through a circular exit as it leaves the laser. in order for the reflected light to be bright enough to detect, the laser spot on the moon must be no more than 1.0 km in diameter. staying within this diameter is accomplished by using a special large-diameter laser. part a if λ = 540nm , what is the minimum diameter of the circular opening from which the laser beam emerges? the earth-moon distance is 384,000 km. express your answer to two significant figures and include the appropriate units.

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.

Using gravity, an elephant can pull a mouse towards it from the ground. true or false explain why. will give brainliest if answered fast and the best explanation