DOUBLE POINTS 1. For athletes, a focus on body mechanics improves the effectiveness of their efforts.
A.
True

B.
False

2. How does Newton’s second law of physics apply to lifting weights?
A.
Lifting weights requires the proper form and net force.
B.
Without force or motion, the weights are an unbalanced force.
C.
It requires more force to move weights, and this builds muscles.
D.
Weights are an immovable object, and the force is provided by muscles.

The focal length of a relaxed human eye is approximately 1.7 cm. when we focus our eyes on a close up object, we can change the refractive power of the eye by about 16 diopters. (a) does the refractive power of our eyes increase or decrease by 16 diopters when we focus closely? explain. (b) calculate the focal length of the eye when we focus closely.

Students design a model roller-coaster track. they place a rubber ball at the highest point on the track and let it go. the ball rolls along the track pulled only by the force of gravity. eventually, it comes to a stop. which change to the design will result in the ball moving the greatest distance?

When a vertical beam of light passes through a transparent medium, the rate at which its intensity i decreases is proportional to i(t), where t represents the thickness of the medium (in feet). in clear seawater, the intensity 3 feet below the surface is 25% of the initial intensity i0 of the incident beam. what is the intensity of the beam "10" feet below the surface? (give your answer in terms of i0. round any constants or coefficients to five decimal places.)