Answer:
(a) 
(b) 
(c) 
Explanation:
(a) According to Newton's second law, the acceleration of a body is directly proportional to the force exerted on it and inversely proportional to it's mass.
(b) According to Newton's third law, the force that the sled exerts on the girl is equal in magnitude but opposite in the direction of the force that the girl exerts on the sled:
(c) Using the kinematics equation:
For the girl, we have 
and 
. So:
For the sled, we have . So:
When they meet, the final positions are the same. So, equaling (1) and (2) and solving for t:
Now, we solve (1) for 
Answer:
a) always. b) electric field lines are defined by the path positive test charges travel.
Explanation:
By convention, field lines always follow the direction that it would take a positive test charge (small enough so it can´t disrupt the field created by a charge distribution), under the influence of an electric field, at the same point where the test charge is located.
So any positive charge, subject to an electric field influence, moves along the field line that passes through its current position, in the same way that a positive test charge would.
We could say also that the electric force on a positively charged particle is in the same direction as the electric field that produces that force (due to some charge distribution) , which is true, but it doesn´t explain why.
Answer:
the number of grains in the ball is 274,848
Explanation:
Given that;
diameter = 0.5 mm
so radius r = 0.25 mm
first we determine the volume of the ball using the following equation;
V = 4/3×πr³
we substitute
V = 4/3×π(0.25)³
V = 0.06544 mm³
Now form table 1.1 "Grain sizes" a metal with grain size number of 12 has about 4,200,000 grains/mm³
so;
Number of grains N = 0.06544 × 4,200,000
N = 274,848 grains
Therefore, the number of grains in the ball is 274,848
Answer:
The new intensity = 3.38 × 10⁻⁵ W/m²
Explanation:
Intensity of sound wave:
The intensity of sound is the rate of flow of flow of energy, per unit area, perpendicular to the direction of the sound wave.
Intensity (I) ∝ A²
where I = intensity, A = Amplitude.
∴ I₁/I₂ = A₁²/A²₂............................... equation 1
From the question, the amplitude increase by 30% of the initial
∴ A₂ = A₁ + 0.3A₁ = 1.3A₁, I₁ = 2.00×10⁻⁵ W/m²
∴ (2.00×10⁻⁵)/I₂ = A₁²/(1.3A₁)²
(2.00×10⁻⁵)/I₂ = 1/1.3²
making I₂ the subject of the equation
I₂ = (2.00 × 10⁻⁵)×1.3² = 3.38 × 10⁻⁵ W/m₂
The new intensity = 3.38 × 10⁻⁵ W/m²
