A28-kg beginning roller skater is standing in front of a wall. by pushing against the wall, she is propelled backward with a velocity of -1.2 m/s. while pushing, her hands are in contact with the wall for 0.80 s. ignoring frictional effects, find the magnitude and direction of the impulse acting on the skater.

Ahollow metal sphere has 6 cm and 11 cm inner and outer radii, respectively. the surface charge density on the inside surface is −100nc/m2. the surface charge density on the exterior surface is:

Does work output exceed work input when a machine is used? a) yes, it does, as machines create energy. b) it depends on the type of machine used. c) no, it doesn’t, as machines are inefficient. d) no, it doesn’t, as machines cannot create energy.

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?