Answer:
Unbalanced forces change the motion of an object. If an object is at rest and an unbalanced force pushes or pulls the object, it will move. Unbalanced forces can also change the speed or direction of an object that is already in motion.
The answer is "False". The force acting on the object is 27 N.
According to Newton's second law, when a force <em>F</em> acts on am object of mass <em>m</em>, it produces an acceleration <em>a</em>. The force is given by the expression,

Thus, if the body has a mass of 9.0 kg and if it has an acceleration of 3 m/s², then, on substituting the values in the equation for force,

Thus, it can be seen that the force acting on the body is 27 N and not 3 N as is mentioned in the statement. Hence the statement is false.
Answer: minimum speed of launch must be 7.45m/s
Explanation:
Given the following:
Height or distance (s) = 2.83m
The final velocity(Vf) at maximum height = 0
Upward motion, acceleration due to gravity(g) us negative = -9.8m/s^2
From the 3rd equation of motion:
V^2 = u^2 - 2gs
Where V = final velocity
u = initial velocity
Therefore, u = Vi
u = √Vf^2 - 2gs
u = √0^2 - 2(-9.8)(2.83)
u = √0 + 55.468
u = √55.468
u = 7.4476 m/s
u = 7.45m/s
Answer:
, 
Explanation:
The magnitude of the electromagnetic force between the electron and the proton in the nucleus is equal to the centripetal force:

where
k is the Coulomb constant
e is the magnitude of the charge of the electron
e is the magnitude of the charge of the proton in the nucleus
r is the distance between the electron and the nucleus
v is the speed of the electron
is the mass of the electron
Solving for v, we find

Inside an atom of hydrogen, the distance between the electron and the nucleus is approximately

while the electron mass is

and the charge is

Substituting into the formula, we find
