An automobile accelerates from rest at 1+ 3* sqrt (t) mph/sec for 9 seconds.
1 answer:
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The force of friction is equal to the pushing force, and the acceleration is zero
Explanation:
In this problem, we are pushing a piano along the floor, in the horizontal direction.
There are 2 forces acting in the horizontal direction on the piano:
- The applied force,
, acting forward
- The force of friction,
, acting backward
Therefore, the net force in the horizontal direction is
According to Newton's second law, the net force is equal to the product between the piano's mass (m) and its acceleration:
Combining the two equations,
However, we are also told that the piano moves at constant speed, therefore the acceleration is zero:
And so,
which means that the force of friction is equal to the applied force.
Learn more about Newton's second law:
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Answer:
1.87 A
Explanation:
τ = mean time between collisions for electrons = 2.5 x 10⁻¹⁴ s
d = diameter of copper wire = 2 mm = 2 x 10⁻³ m
Area of cross-section of copper wire is given as
A = (0.25) πd²
A = (0.25) (3.14) (2 x 10⁻³)²
A = 3.14 x 10⁻⁶ m²
E = magnitude of electric field = 0.01 V/m
e = magnitude of charge on electron = 1.6 x 10⁻¹⁹ C
m = mass of electron = 9.1 x 10⁻³¹ kg
n = number density of free electrons in copper = 8.47 x 10²² cm⁻³ = 8.47 x 10²⁸ m⁻³
= magnitude of current
magnitude of current is given as
= 1.87 A