Complete question:
new concrete mix is being designed to provide adequate compressive strength for concrete blocks. The specification for a particular application calls for the blocks to have a mean compressive strength µ greater than 1350 kPa. A sample of 100 blocks is produced and tested. Their mean compressive strength is 1356 kPa and their standard deviation is 70 kP
a) Find the p value.
b) Do you believe it is plausible that the blocks do not meet the specification, or are you convinced that they do? Expain your reasoning.
Answer:
a) p-value= 0.1949
b) It is possible the blocks do not meet the specifications
Explanation:
Given:
n = 100
Sample mean, X' = 1356
Standard deviation, s.d = 70
a) To find p- value.
Null hypothesis:
H0: u ≤ 1350
Alternative hypothesis:
H1 : u > 1350
The test statistic wll be:
=0.86
The p value will be:
= P(z>0.86)
= 1-P(z≤0.86)
Using the normal distribution table, we now have:
1 - 0.8051
= 0.1949
P value = 0.1949
b) Since our p-value is 0.1949, we do not reject the null hypothesis, because the p-value, 0.1949, is not small. This means that it is possible the blocks do not meet the specifications.
E force needed to accelerate a 68 kilogram-skier at a rate of
1.2
m
s
2
is 81.6 Net forces.
Explanation:
Take the mass(68kg) and the acceleration of the skier(
1.2
m
s
2
) and multiply them together
<span>Cell membranes are selectively permeable because it allows some things to enter or leave the cell while keeping other things outside or inside the cell.</span>
Answer: apparent weighlessness.
Explanation:
1) Balance of forces on a person falling:
i) To answer this question we will deal with the assumption of non-drag force (abscence of air).
ii) When a person is dropped, and there is not air resistance, the only force acting on the person's body is the Earth's gravitational attraction (downward), which is the responsible for the gravitational acceleration (around 9.8 m/s²).
iii) Under that sceneraio, there is not normal force acting on the person (the normal force is the force that the floor or a chair exerts on a body to balance the gravitational force when the body is on it).
2) This is, the person does not feel a pressure upward, which is he/she does not feel the weight: freefalling is a situation of apparent weigthlessness.
3) True weightlessness is when the object is in a place where there exists not grativational acceleration: for example a point between two planes where the grativational forces are equal in magnitude but opposing in direction and so they cancel each other.
Therefore, you conclude that, assuming no air resistance, a person in this ride experiencing apparent weightlessness.
The phases of the moon are the changing appearances of the moon, as seen from Earth. Which phase happens immediately after a third quarter moon are the following
Explanation:
- After the full moon (maximum illumination), the light continually decreases. So the waning gibbous phase occurs next. Following the third quarter is the waning crescent, which wanes until the light is completely gone -- a new moon.
waning gibbous phase
- The waning gibbous phase occurs between the full moon and third quarter phases. The last quarter moon (or a half moon) is when half of the lit portion of the Moon is visible after the waning gibbous phase.
Time takes by the moon to go through all the phases
about 29.5 days
- It takes 27 days, 7 hours, and 43 minutes for our Moon to complete one full orbit around Earth. This is called the sidereal month, and is measured by our Moon's position relative to distant “fixed” stars. However, it takes our Moon about 29.5 days to complete one cycle of phases (from new Moon to new Moon).
- At 3rd quarter, the moon rises at midnight and sets at noon. Then we see only a crescent. At new, the moon rises at sunrise and sets at sunset, and we don't see any of the illuminated side!