The sun is 60° above the horizon. Rays from the sun strike the still surface of a pond and cast a shadow of a stick that is stuc
k in the sandy bottom of the pond. If the stick is 19 cm tall, how long is the shadow?
1 answer:
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The chair does not move along the vertical direction: this means that the net force on the vertical direction is zero.
There are three forces acting along the vertical direction:
- The weight, acting downward:
- The component of the force F perpendicular to the floor, acting downward:
- The normal force N, acting upwards.
Since the net force must be zero, we have:
From which we can find the value of N:
Answer:
C. Why you must push harder to move a car farther.
Explanation:
Newton's Second Law of Motion states that the acceleration of a physical object is directly proportional to the net force acting on the physical object and inversely proportional to its mass.
Mathematically, it is given by the formula;
Hence, Newton's 2nd Law explains why you must push harder to move a car farther because of its mass. Thus, it is important to increase the force that the engine provides and decrease the mass of the car.
Answer:
The tension is 75.22 Newtons
Explanation:
The velocity of a wave on a rope is:
(1)
With T the tension, L the length of the string and M its mass.
Another more general expression for the velocity of a wave is the product of the wavelength (λ) and the frequency (f) of the wave:
(2)
We can equate expression (1) and (2):
=
Solving for T
(3)
For this expression we already know M, f, and L. And indirectly we already know λ too. On a string fixed at its extremes we have standing waves ant the equation of the wavelength in function the number of the harmonic is:
It's is important to note that in our case L the length of the string is different from l the distance between the pin and fret to produce a Concert A, so for the first harmonic:
We can now find T on (3) using all the values we have: