Refer to Concept Simulation 4.4 for background relating to this problem. The drawing shows a large cube (mass = 28.9 kg) being a
1 answer:
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Answer:
b.A single force acts on the object.
Explanation:
Newton's first law establishes that an object at rest remains at rest and an object in motion will have constant velocity if the result of the forces acting on them is zero
An object acceleration can be defined as the variation of velocity in an interval of time:
(1)
Where is the final velocity,
is the initial velocity,
is the final time and
is the initial time.
If the velocity is constant there is no variation of velocity, therefore, the acceleration will be 0.
Newton's second law can be used To show that no forces act on the object:
(2)
Where R is the resultant of all the forces, m is the mass and a is the acceleration.
Since there is no acceleration for an object with constant velocity, equation (2) can be expressed as:
So it is correct to say that an object with constant velocity has no forces acting on it.
In the other hand in the case of several forces acting on the object, The net force (R) can be zero if they have the same magnitude and opposite direction
So (a), (c) and (d) are correct because of what was previously discussed.
<u>Note that b cannot be true since it violates Newton's first law, since the object is moving at a constant velocity. </u>
Answer:
a) Bullet will hit
b) Bullets will not hit
Explanation:
Given:
The velocity of the bullet, u = in the rest frame of the bullet pursuit car
The velocity of the original frame of reference, v = with respect to the pursuit car.
Now, according to the Galileo
the velocity of the bullet in the original frame of reference (u') will be
u' = u - v
on substituting the values we get
u' =
or
u' =
or
u' =
since this velocity ( ) is greater than the (
)
hence,
<u>the bullet will hit</u>
Now, according to the Einstein theory
the velocity of the bullet in the original frame of reference (u') will be
on substituting the values we get
or
or
since,
is less than (
), this means that the bullet will not hit
<h2>Hello!</h2>
The answer is C. The television uses 6,588,000 J less than the lamp.
<h2>Why?</h2>First, we must know that 1 Wh( Watt consumed in 1 hour) = 3600 J
Wh is the unit that express the energy amount of consumed in 60 minutes/ 1 hour.
So,
From the enunciate information we can calculate the energy consumed by the lamp and the television.
For the lamp, we have that it left on for 24 hours and it has a power of 120
For the television, we have that it left on for 3 hours and it has a power of 350W
Calculating the energy consumed (Wh) we have:
and converting it to Joule, we have:
Doing the same for the television, we have:
and converting it to Joule, we have:
Finally, we have
:
Then having calculated both consume, we have that the television uses 6,588,000 J less than the lamp.