At a soccer practice, the players run sprints. they start at the goal, run 10 m toward the center of the field and then run back to the goal. then they run 20 m toward the center of the field and back to the goal. finally they run 30 m toward the center of the field, turn around, and run back to the goal again. one player times herself to try and beat her personal best time. she runs the first 10 m in 2.5 s and gets back to the goal in 2.8 s. then she runs the 20-m sprint in 5.7 s and gets back to the goal in 6.7 s. she runs the final 30-m sprint in 12 s and gets back to the goal in 15 s. what was her average speed for the entire exercise? 3.0 m/s 2.5 m/s 2.7 m/s 0 m/s

0 m/s

Explanation:

Remember that in physics we have something called distance and displacement, average speed for a certain number of movements is given by the next formula:

As you can see she ended up in the same spot from where she started so her displacement was actually 0, since the displacement is 0 the average speed will also be 0. So she had a 0 m/s average speed.

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27