They do the method 3 times to be sure. Because if you do it once, that could mean anything. If you do it twice, it may or may not have the same result. If you do it 3 times and it matches one of the previous answers, then it's likely that it's correct.
The answer to this question would be: a spring scale.
The spring scale that you use to determine your body weight is actually a device that measures your body gravitational force. The force itself influenced by your body weight, that is why it can determine your body weight.
More weight means more force, more force will shrink the spring more.
Answer:
The force is 
Explanation:
Given that,
Mass of car = 64 kg
Suppose, a 1400-kg car that stops from 34 km/h on a distance of 1.7 cm.
We need to calculate the acceleration
Using formula of acceleration

Where, v = final velocity
u = initial velocity
a = acceleration
s = distance
Put the value into the formula



We need to calculate the force
Using formula of force



Negative sign shows the direction of the force is in the direction opposite to the initial velocity.
Hence, The force is 
The displacement of the bird is 1.8 km...because displacement is the distanse of the object from mean position to the travelled position.....hope it helps
Diffuse reflection have a great day