A 1.3-kg block is pushed up against a stationary spring compressing it a distance of 4.2 cm. When the blocks spring is released, the spring pushes it away across a friction less horizontal surface. What is the speed of the block, given that the spring constant is 1400 N/m

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it

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auroras are generated by charged solar particles hitting molecules in earth's atmosphere. this usually happens in high latitudes, because our planet’s magnetic field tends to funnel these particles toward the poles. that’s why it can be experienced in northern ohio.