Answer:
Bottom of the circle.
Explanation:
At the top of the circle the tension and the weight contribute on being the centripetal force, at the middle of the circle only the tension contributes on being the centripetal force (the weight being perpendicular to it), while <u>at the bottom</u> of the circle the tension contributes on being the centripetal force (as always) <em>but the weight against to it</em>, so here is where the tension must be greater to allow the same centripetal force as the other cases, thus here is where the string will break.
D. A magnetic field created by the electric current causes the compass needle to move.
Explanation:
Given that,
Mass of the object, m = 7.11 kg
Spring constant of the spring, k = 61.6 N/m
Speed of the observer, 
We need to find the time period of oscillation observed by the observed. The time period of oscillation is given by :

Time period of oscillation measured by the observer is :

So, the time period of oscillation measured by the observer is 5.79 seconds.
<span>Answer: The acceleration of 10 kg object is greater than that of 18 kg object.
Explanation:
According to Newton's Second law:
F = ma --- (A)
Let's find the acceleration for both 10 kg and 18 kg objects!
The net force on both of these masses = F = 20N
(1) Acceleration of 10 kg object
Mass = m = 10 kg
Plug in the values in equation (A):
20 = 10 * a
Acceleration = a = 2 m/s^2
(2) Acceleration of 18 kg object
Mass = m = 18 kg
Plug in the values in equation (A):
20 = 18 * a
Acceleration = a = 1.11 m/s^2
2 > 1.11; therefore, 10 kg object has the higher acceleration compared to the acceleration of the 18 kg object.</span>