True.
A contact force is a force between two objects that are physically in contact with each other: an example of a contact force is the normal reaction of a table supporting a book.
A non-contact force is a force between two objects that are not physically in contact with each other: an example of non-contact force is the gravitational attraction between the Earth and the Moon.
Explanation:
It is given that,
Spring constant of the spring, k = 15 N/m
Amplitude of the oscillation, A = 7.5 cm = 0.075 m
Number of oscillations, N = 31
Time, t = 15 s
(a) Let m is the mass of the ball. The frequency of oscillation of the spring is given by :

Total number of oscillation per unit time is called frequency of oscillation. Here, 


m = 0.0895 kg
or
m = 89 g
(b) The maximum speed of the ball that is given by :





Hence, this is the required solution.
1-a 2-b 3-b
srry had to write more, i go to this school
Hi there!
We know that:
Force due to gravity = Mgsinθ
Force due to friction = μMgcosθ
Let the positive direction be directed in the direction of the block's acceleration, which is downward.
Thus:
ΣF = Mgsinθ - μMgcosθ
Solving for acceleration requires diving all terms by the mass, so:
a = gsinθ - μgcosθ
Substitute in given values. (g = 9.8 m/s²)
a = 9.8sin(30) - 0.3(9.8)cos(30) = 2.354 m/s²
F = kq1q2/r^2
<span>q1 is first charge </span>
<span>q2 is second charge </span>
<span>k is 9 E9 </span>
<span>r is distance between them </span>
<span>F = (9E9)(2 E-6)(4 E-6)/2^2 = 0.018 N </span>
<span>A postive answer indicates a repulsive force</span>