Jack and Rose wanted to study the effects of friction on the motion of objects. In order to do so, they decided that they would test how well a coin slides across various surfaces with different amounts of friction. The surfaces that they slid the coin across were: a smooth white board, a piece of textured fabric, and a piece of sandpaper. In order to guarantee that the amount of force applied remained constant, the surfaces were placed on top of a book and kept at a 50 degree angle the entire time. The penny was placed on its side at the top of the surface and allowed to slide down. The distance the penny slid down the surface was measured after each trial and recorded in the data table. Distance the Penny Slid:
Material
Trial 1
Trial 2
Trial 3
White Board
31 cm
32 cm
31.5 cm
Textured Fabric
22 cm
21.5 cm
22 cm
Sandpaper
3 cm
2 cm
1.5 cm

Directions: Write a CER / Explanation for the experiment explained above, as if you were one of the experimenters.

Search coils and credit cards. one practical way to measure magnetic field strength uses a small, closely wound coil called a search coil. the coil is initially held with its plane perpendicular to a magnetic field. the coil is then either quickly rotated a quarter-turn about a diameter or quickly pulled out of the field. (a) derive the equation relating the total charge q that flows through a search coil to the magnetic-field magnitude b. the search coil has n turns, each with area a, and the flux through the coil is decreased from its initial maximum value to zero in a time ∆t. the resistance of the coil is r, and the total charge is q = i∆t, where i is the average current induced by the change in flux. (b) in a credit card reader, the magnetic strip on the back of a credit card is rapidly “swiped” past a coil within the reader. explain, using the same ideas that underlie the operation of a search coil, how the reader can decode the information stored in the pattern of magnetization on the strip. (c) is it necessary that the credit card be “swiped” through the reader at exactly the right speed? why or why not?

Who was the first scientist to measure speed as distance over time?

Two carts, one of mass 2m and one of mass m, approach each other with the same speed, v. when the carts collide, they hook together. assume that positive momentum is to the right. which graph best represents the momentum of both carts over time, before and after the collision?