A force of 20 N acts upon a block moving at 4 m/s. calculate the mass of the object
1 answer:
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1. +72.0 kg m/s
The momentum of an object is given by:
p = mv
where
m is the mass of the object
v is its velocity
Taking "to the right" as positive direction, for Elena we have
m = 60.0 kg is the mass
v = +1.20 m/s is the velocity
So, Elena's momentum is
2. -162.5 kg m/s
Here Madison is moving in the opposite direction of Elena (to the left), so her velocity is
v = -2.50 m/s
while her mass is
m = 65.0 kg
Therefore, her momentum is
3. -90.5 kg m/s
The total momentum of Elena and Madison is equal to the algebraic sum of their momenta; taking into account the correct signs, we have:
4. 0.72 m/s to the left
We can find the final speed of Elena and Madison by using the law of conservation of momentum. In fact, the final momentum must be equal to the initial momentum (before the collision).
The initial momentum is the one calculated at the previous step:
while the final momentum (after the collision) is given by
where
is Elena's mass
is Madison's mass
v is their final velocity
According to the law of conservation of momentum,
So we can find v:
and the direction is to the left, since the sign is negative.
(A) We can solve the problem by using Ohm's law, which states:
where
V is the potential difference across the electrical device
I is the current through the device
R is its resistance
For the heater coil in the problem, we know
and 
, therefore we can rearrange Ohm's law to find the current through the device:
(B) The resistance of a conductive wire depends on three factors. In fact, it is given by:
where
is the resistivity of the material of the wire
L is the length of the wire
A is the cross-sectional area of the wire
Basically, we see that the longer the wire, the larger its resistance; and the larger the section of the wire, the smaller its resistance.
where
V is the potential difference across the electrical device
I is the current through the device
R is its resistance
For the heater coil in the problem, we know
(B) The resistance of a conductive wire depends on three factors. In fact, it is given by:
where
L is the length of the wire
A is the cross-sectional area of the wire
Basically, we see that the longer the wire, the larger its resistance; and the larger the section of the wire, the smaller its resistance.
Answer:
Decreases by times
Explanation:
The intensity of a sound is defined as the energy of the sound that is flowing in an unit time through the unit area which is in the direction that is perpendicular to the direction of the sound waves movement.
The intensity of energy is described by the inverse square law. It states that the intensity varies inversely with the distance square of the distance.
In other words, the sound intensity decreases as inversely proportional to the squared of the distance. i.e.
In the context when the distance was 3 m, the intensity of the sound was =
But when the distance became 6 cm or 0.06 m, the sound intensity decreases by =
= times