Recent content by Heidi M

By the way, I am so impressed with the expert advice and prompt responses on this site. Thanks again, and thanks a million!

Thanks for all of your help and for your clear explanations. I appreciate it.

The problem states: "Assume that one thousand years from now a Transporter exists that reduces people and things to data (elementary bits of information) and transmits the data by light or radio signal to remote locations. There a Receiver uses the data to reassemble travelers and their...

I'm fulfilling my life-long dream of learning relativity theory by working through Taylor and Wheeler's Spacetime Physics. I've successfully made it through the first three chapters except for one problem, 1-10 on p. 23: Samantha is beamed from Earth via a transporter to the planet...

Of course it was dragged out for so long...because of my mistake! Glad you've got it all figured out.

(2m)(sin30)=1m. 2m (the compression distance) is the hypotenuse.

Ki is zero because the problem states that the block is "released." So you assume it starts from rest. You make the choice to set the zero level for gravitational potential energy at the block's lowest altitude (you don't have to), so Uf will be zero.

Note: when the block first hits the spring its altitude will be 1 m and its gravitational potential energy will be mgh = 10x9.81x1 J.

Oops. When the block first hits the spring it will have gravitational potential energy as well as kinetic. That 200 J of energy is divided into 101.9 J of kinetic and 98.1 J of potential, giving a speed of 4.5 m/s.

You need use only energy conservation. At the bottom of the incline: energy lost by the block as the spring slows it to a stop (the block's kinetic energy at the bottom of the incline) = energy gained by the spring = (1/2)(100N/m)(2m)^2 = 200J As the block slides down the incline: energy at...

Elastic PE stored in compressed spring is (1/2)kx2=(1/2)(100N/m)(2m)2=200J. This is the KE of block at bottom of incline because this is the amount of energy that the block loses in compressing the spring. The block gains KE in the amount mgh as it slides down incline. mgh = 200J, h=2.04 m...

Also, Richard Wolfson's "Simply Einstein: Relativity Demystified"

Definitely John A. Wheeler's "Spacetime Physics"