Answer:
470 N.
Explanation:
Using equations of motion:
S = vi*t + 1/2*(a*(t^2))
Given:
S = 0.65 m
t = 1.5 s
vi = 0 m/s
0.65 = 1/2 * (a * (1.5)^2)
a = 1.3/2.25
= 0.578 m/s^2
Force = mass * acceleration due to gravity
= 92 * 0.578
= 53.16 N
Total force = 420 + 53.16
= 473.16 N
= 470 N.
<span>The weight of the rock is 138n when accelerating downward at 3.5m/ s2.Weight is a measurement of the force of gravity on an objects mass. Therefore as long as the force of gravity is the same and the mass of the rock is the same the weight should also be the same.</span>
Answer: A. All of the answers are correct.
Number 20 is B and 21 is C
Answer:
P = 1471500 [Pa]
Explanation:
We must remember that pressure is defined as the relationship between Force over the area.

where:
P = pressure [Pa] (units of pascals)
F = force [N] (units of Newtons)
A = area of contact = 4 [cm²]
But first we must convert from cm² to m²
![A = 4[cm^{2}]*\frac{1^{2} m^{2} }{100^{2} cm^{2} }](https://tex.z-dn.net/?f=A%20%3D%204%5Bcm%5E%7B2%7D%5D%2A%5Cfrac%7B1%5E%7B2%7D%20m%5E%7B2%7D%20%7D%7B100%5E%7B2%7D%20cm%5E%7B2%7D%20%7D)
A = 0.0004 [m²]
Also, the weight should be calculated as follows:

where:
m = mass = 60 [kg]
g = gravity acceleration = 9.81 [m/s²]
Now replacing:
![w = 60*9.81\\w = 588.6[N]](https://tex.z-dn.net/?f=w%20%3D%2060%2A9.81%5C%5Cw%20%3D%20588.6%5BN%5D)
And the pressure:
![P=588.6/0.0004\\P=1471500 [Pa]](https://tex.z-dn.net/?f=P%3D588.6%2F0.0004%5C%5CP%3D1471500%20%5BPa%5D)
Because 1 [Pa] = 1 [N/m²]