In winter why do water tanks start freezing from surface and not from bottom

Two identical massless springs of constant k = 200N/m are fixed at opposite ends of a level track, as shown. A 5 kg block is pressed against the left spring, compressing it by 0.15m. The block is then released from rest.

Which coordinate system would be most useful for two observers (one in Michigan and one in Florida) who wants to observe the same astronomical object and discuss their observations over the phone as they're making them? a.

How is it that substances can have the same chemical formulas but make different types of matter?

A bullet of 10g strikes a sand bag at a speed of 100 m/s and gets embedded after travelling 5 cm inside the bag. Calculate the resistive force exerted by the sand on the bullet and the time taken by the bullet to come to rest. with calculation

The distance between the sun and earth is about 1.5*10^11m. express this distance with an SI prefix and in kilometer

Which of the following could you do to increase the strength of an electromagnet?

A car accelerates from 13 m s to 25 m s in 6.0 s. what was its acceleration? how far did it travel in this time? assume constant acceleration.

How much elastic potential energy is stored in a bungee cord with a spring constant of 10.0 N/m when the cord is stretched 2.00 m?

Which of the following criteria do astronomers use to classify an object as a planet? orbits a star gravity makes spherical at least as large as mercury clears orbits of other objects

Imagine a 15 kg block moving with a velocity of 20 m/s to the left. Calculate the kinetic Energy of this block. Show the equation, your work, and the answer with units: