Answer:
1.40 N
Explanation:
The magnitude of the frictional force is given by:

where
is the coefficient of friction
N is the magnitude of the normal reaction
The coefficient of friction for this problem is
. The magnitude of the normal reaction is equal to the combined weight of the boy and the sled, because the surface is horizontal, so

Therefore, the frictional force is

Answer:
t = 0.04159 s
Explanation:
when a capacitor and resister are connected in series. charge on its plates decreases exponentially

where,
CHARGE q =15.0 C
INITIAL CHARGE q_0 = 30.0 uc
Resistor R = 20.0 F
capacitor C = 3.00

t = 0.04159 s
Answer:
The period of motion is 0.5 second.
Explanation:
Given;
extension of the spring, x = 3.8 cm = 0.038 m
mass of the object, m = 13 g = 0.013 kg
Determine the force constant of the spring, k;
F = kx
k = F / x
k = mg / x
k = (0.013 x 9.8) / 0.038
k = 3.353 N/m
When the object is replaced with a block of mass 20 g, the period of motion is calculated as;

Therefore, the period of motion is 0.5 second.
Answer:
when a person is not breathing
Explanation:
The electrocardiogram shows the cardiac action of the heart as a means of the sinusoidal waves. However, the waves have a different structure as they show the pumping phase, breathing and the resting phase of the heart. The waves continues to be displayed as long as there is systolic and diastolic pressure in the heart muscles. When there is no action, such as the cessation of brain activity, action ceases.