Semester 1, part 2 assessment
it’s time to take the teacher-scored semester assessment. save the semester assessment to your computer with the correct unit name, unit number, lesson number, and your name at the end of the file name (e. g., offline_test
_u1l4_alice_jones. doc). when you have finished, use the dropbox tool to submit your completed semester assessment to your teacher.
1. explain why elements with a completely full outer shell of electrons do not usually bond with other elements to form compounds. (10 points)
2. a cyclist pedals his bike and reaches the top of a hill. then he begins to coast downhill without pedaling. when he reaches the bottom of the hill, he again applies force to the pedals. explain why the cyclist accelerates as he coasts downhill. (10 points)
3. rick put a drinking straw into a glass of water. when he looked at the side of the glass, the straw appeared to be broken. explain this observation. (10 points)
science | semester 1, part 2 assessment

grav force prop 1/r squared 2r all squared is 4rsquared 1/4rsquared quartered

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.