In which situation is the object experiencing unbalanced forces? A) A box resting on a horizontal floor. B) A car slowing as it
2 answers:
Answer:
B) A car slowing as it reaches a traffic light.
Explanation:
Newton's second law states that an object which experiences unbalanced forces has an acceleration, according to the equation:
where
F is the net force acting on the object
m is its mass
a is its acceleration
When the forces are unbalanced, it means that the net force F is different from zero, so the acceleration of the object (a) is also different from zero.
Now let's analyze each situation:
A) A box resting on a horizontal floor. --> The object is at rest, so it is not accelerating. This means that the forces acting on it are balanced (net force = 0), so this is not the correct choice
B) A car slowing as it reaches a traffic light. --> The car is slowing down, this means that it has an acceleration: therefore, it is experiencing unbalanced forces. So, this is the correct choice.
C) A car with its cruise control set to 30 km/h. --> The car is moving at constant velocity, so it has zero acceleration. This means that the forces acting on it are balanced (net force = 0), so this is not the correct choice
D) A penny at terminal velocity after falling off of a building. --> The penny is at terminal velocity, which means that it is moving at constant velocity, so it has zero acceleration. This means that the forces acting on it are balanced (net force = 0), so this is not the correct choice.
Therefore, the correct choice is
B) A car slowing as it reaches a traffic light.
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Answer:
24.71 mm
Explanation:
Distance is proportional to focal length, so
d∝f
which means
Magnification of first lens
and
Similarly, magnification of second lens
and
From the above equations we get
and
which means,
and
So, we get
∴ Focal length should this camera's lens is 24.71 mm
Answer:
The heat transferred from water to skin is 6913.5 J.
Explanation:
Given that,
Weight of water = 25.0 g
Suppose that water and steam, initially at 100°C, are cooled down to skin temperature, 34°C, when they come in contact with your skin. Assume that the steam condenses extremely fast. We will further assume a constant specific heat capacity c=4190 J/(kg°K) for both liquid water and steam.
We need to calculate the heat transferred from water to skin
Using formula for stream
Put the value into the formula
Hence, The heat transferred from water to skin is 6913.5 J.