Answer:
118 N
Explanation:
Given mass of the block, m = 4.00kg.
The acceleration of the elevator, a = 3.0 m/s^2.
As elevotar attaced with spring scale and accelerating upward
(block and elevator), so total force

Here, mg is the weight of the block downward direction.
or

substitute the given value, we get

= 117.6 N = 118 N.
Thus, the reading on the spring scale to 3 significant figures is 118 N.
The centripetal force : F = 293.3125 N
<h3>Further explanation</h3>
Given
mass = 65 kg
v = 9.5 m/s
r = 20 m
Required
the centripetal force
Solution
Centripetal force is a force acting on objects that move in a circle in the direction toward the center of the circle

F = centripetal force, N
m = mass, Kg
v = linear velocity, m / s
r = radius, m
Input the value :
F = 65 x 9.5² / 20
F = 293.3125 N
Answer: m = 0.035kg = 35g
Explanation: Momentum p=0.140kgm/s
Velocity v=4m/s
Mass m=?
Formula-
Momentum depends on the mass of the object in motion and its velocity.
The equation for momentum is
p = mv
m = p/v
m = 0.140/4
m = 0.035kg
m = 35g
Hence, in the toy dart gun mass of the dart is 0.035kg.
Answer:
a)The approximate radius of the nucleus of this atom is 4.656 fermi.
b) The electrostatic force of repulsion between two protons on opposite sides of the diameter of the nucleus is 2.6527
Explanation:

= Constant for all nuclei
r = Radius of the nucleus
A = Number of nucleons
a) Given atomic number of an element = 25
Atomic mass or nucleon number = 52


The approximate radius of the nucleus of this atom is 4.656 fermi.
b) 
k=
= Coulombs constant
= charges kept at distance 'a' from each other
F = electrostatic force between charges


Force of repulsion between two protons on opposite sides of the diameter



The electrostatic force of repulsion between two protons on opposite sides of the diameter of the nucleus is 2.6527

Actually Welcome to the Concept of the Projectile Motion.
Since, here given that, vertical velocity= 50m/s
we know that u*sin(theta) = vertical velocity
so the time taken to reach the maximum height or the time of Ascent is equal to
T = Usin(theta) ÷ g, here g = 9.8 m/s^2
so we get as,
T = 50/9.8
T = 5.10 seconds
thus the time taken to reach max height is 5.10 seconds.