Can a magnet attract a pure substance?

Astudent is given an assignment to demonstrate diffraction. he takes a photograph of a straw in a glass of water. the straw appears bent at the water level. which best describes this example? a) this is a good example of diffraction. b) this is an example of dispersion and not diffraction. c) this is an example of refraction and not diffraction. d) this is an example of reflection and not diffraction.

You have two photos of a person walking. one shows the person at the corner of third and main streets, the other shows the person at the corner of tenth and main streets. there are lampposts at every corner in this town, and the first picture shows it to be 10: 32: 00 exactly. the second picture shows it to be 10: 49: 30. you know three facts: (1) all of the clocks are synchronized; (2) there are exactly 12 equal-sized blocks per kilometer in this town; and (3) the streets that cross main in this area are numbered consecutively, with no interruptions. what is the person’s average speed in kilometers per hour?

You are your friend move a new refrigerator into his kitchen. you apply a horizontal force of 252 n in the negative x direction to try and move the 56 kg refrigerator. the coefficient of static friction is 0.61. (a) how much static frictional force does the floor exert on the refrigerator? give both magnitude (in n) and direction. magnitude n direction (b) what maximum force (in n) do you need to apply before the refrigerator starts to move?