Answer: Bohr's model
Explanation:
The Bohr's model is also known as the solar system model which describe that an atoms are basically imagine in the form of solar system. The Bohr's model basically describe about the atoms that it consist of nucleus with the number of electron in an orbit by using the electrostatic attraction.
The Bohr's model are introduced for overcoming the drawback in the Rutherford model as he proposed an idea that at different energy levels the electron can revolve in certain orbits around nucleus.
Answer:
W= - 1414.48 J : Work done by the friction force on the box.
Explanation:
Work concept
The work (W) of a given force is defined as the product of the force (F) by the distance(d) in which the force acted.
W= F*d :in (Joules) Formula (1)
Friction force concept
Ff=μk*N Formula (2)
μk=coefficient of kinetic friction
N= Normal force
We apply Newton's first law for forces in the direction of the axis y
∑Fy=0 Equation (1)
The forces acting on the box in the direction of the axis and are the following:
- Fy=Force of 210 N in y= 210*sen 39°= 132.16 N ( +y)
- W=Weight of box= m*g=30kg*9.8m/s² = 294N (-y)
- N =Normal force ( +y)
We apply equation (1) and do the algebraic sum of forces in y
Fy+N-W=0
132.16+N-294=0
N= 294-132.16=161.84 N
We apply formula (2) to calculate Ff:
Ff= -0.23*161.84=-37,22N The frictional force is negative because it goes in the opposite direction to the displacement.
We apply formula (1) to calculate the work done by the friction force on the box
W= - 37,22 N * 38 m = -1414.48 N*m = -1414.48 J
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Answer: A
Explanation: We know that f=p*n
f=50*300=15000 Hz = 15kHz.
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