Why must humans limit their exposure to X-rays and gamma rays?
2 answers:
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Answer:
a) Fg = -27.4 N
b) Fnet = 5.2 N
c) a = 1.9 m/s2
Explanation:
a)
- There are two forces acting on the ball, one directed upward (assuming this direction as positive, along the y-axis) which is the tension on the string (lifting force), and another aimed downward, which is the attractive force due to gravity.
- Applying the Newton's Universal Law of Gravitation to a mass close to the surface of the Earth (in this case the ball), we can take the acceleration due to gravity like a constant, that we call by convention g, equal to -9.8 m/s2.
- So, we can write the following expression for Fg:
b)
- The net force on the ball, will be just the difference between the lifting force (32.6 N) and the force due to gravity, Fg:
c)
- According Newton's 2nd Law, the acceleration caused by a net force on a point mass (we can take the ball as one) is given by the following expression:
The velocity of the object is zero (the object is at rest)
Explanation:
A position vs time graph represents the motion of an object; in particular:
- The position of the object x(t) is represented on the y-axis
- The time t is represented on the x-axis
For a position-time graph, the slope of the graph is given by
where
is the change in position
is the change in time
However, we see that this is equivalent to the definition of velocity:
Therefore, the slope of a position-time graph is equivalent to the velocity of the object.
And so, a horizontal segment on a position vs time graph means that the object has zero velocity (because the slope is zero).
Learn more about velocity:
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