Physics #2

For this post, I'm going to post questions from the textbook

Page 376
Question 12: The traffic sign at the beginning of a school zone reads "30 km/h" Is this sign a 'speed zone' sign or a 'velocity zone' sign? explain your answer.
Answer: To me, the sign in a 'speed zone' sign. This is because the sign only tell the speed, and not the direction the car needs to go.
Question 16: The SI unit for average speed or average velocity is m/s. What is another common unit used for these two concepts?
Answer: Another common unit is km/h
Page 377
Question 20: A girl rides her bike 420m south in time of 47s. What is her average velocity?
Answer: V=d/t, V=420/47, V=9m/s
Page 391
Question 8: A) If the acceleration is in the same direction as the velocity, what happens to the speed of an object
Answer: The speed of the object will increase
B) If the acceleration is in the opposite direction to the velocity, what happens to the speed of an object?
Answer: The speed of an object will decrease.
 Question 9: A car traveling forward at 25m/s stops and backs up at 4m/s
A) What is the car's change in velocity?
Answer: The change in velocity is 21m/s
B) What is the direction of the car's acceleration?
Answer: Backward
Page 397
Question 1: A car starting from rest accelerates uniformly to 15m/s [E] in 5s. What is the car's acceleration?
Answer: A=^V/t, A=15m/s / 5s, A=3m/s2 [E]
Page 405
Question 2: What does the slope of a velocity-time graph represent?
Answer: The slope represents the acceleration of an object.
Question 6: In the absence of air resistance, what is the magnitude and direction of the acceleration due to gravity near the surface of Earth?
Answer: The acceleration due to gravity is 9.8m/s2 downward.
Question 8: What is the acceleration of a golf ball that is accelerated uniforly from rest 55m/s forward in 0.00045s?
Answer: A=^V/t, A=55/0.00045, A=12222.23m/s2

I thought these questions were important to the unit because it shows air resistance, gravity, the slope, and equations. If I didn't know how to factor in all of these, and to do the equations, I wouldn't have been able to pass the unit, or understand what my teacher was talking about, and luckily I did.