Answer: a. both reliable and valid
The parameters used to describe a particular trait or characteristic in a human behavior should be reliable and valid, in order to determine the response of the population with respect to a particular stimulus.
Answer: To isolate the unknown substances, of which only tiny amounts were present, the Curies were the first to use a new method of chemical analysis. They employed various standard (but sometimes demanding) chemical procedures to separate the different substances in pitchblende.
Explanation:
Answer:
A) and B) are correct.
Explanation:
If the object is at rest, it means that no net force is exerted on it.
As the object experiences a downward gravitational force from Earth, in order to be at rest, it must experience an upward force with the same magnitude as the gravitational force on the object.
This force is supplied by the normal force, which can adopt any value in order to meet the condition imposed by Newton´s 2nd Law, and is always perpendicular to the surface on which the object is placed (in this case, the ground).
At a molecular level, this normal force is supplied by the bonded molecules of the ground that behave like small springs being compressed by the molecules of the object, exerting an upward restoring force upward on them.
So, the statements A) and B) are true.
a) The velocity of the boat relative to the shore is 3.40 m/s and b) The position of the boat relative to its point of origin after 3s is 10.20m.
Here it is given that the speed of the boat (x) = 2.20m/s
The speed of the stream current (y) = 1.20m/s
a) We have to find the velocity of the boat relative to the shore.
The speed of the boat = x + y
= 2.20 + 1.20
= 3.40m/s
b) Now we have to find the position of the boat after 3s
The formula for speed:
Speed = Distance/ Time
distance = speed × time
speed = 3.40m/s
Time = 3s
distance = 3.40 × 3
= 10.20 m
Therefore we get a) speed as 3.40m/s and b) distance as 10.20m.
To know more about the boat and stream refer to the link given below:
brainly.com/question/382952
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Weight = (mass) x (acceleration of gravity) .
On Earth, acceleration of gravity is 9.8 m/s² (rounded) .
650 N = (mass) x (9.8 m/s²)
Divide each side by (9.8 m/s²): 650 N / 9.8 m/s² = mass
Mass = 66.3 kilograms (rounded)
