determine the pressure exerted on the surface of a submarine cruising 175 ft below the free surface of the sea. assume that the
1 answer:
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b) the net force on the car is zero.
Explanation:
Let's analyze each option one by one:
a) the force from the engine is greater than all the forces of friction. --> FALSE. In fact, the car is moving at constant velocity: this means that its acceleration is zero,
a = 0
and so Newton's second law becomes
where is the net force on the car and m is its mass. This means that the net force on the car is zero: so, the force from the engine cannot be greater than all the forces of friction, otherwise the net force cannot be zero.
b) the net force on the car is zero. --> TRUE, for what we said at point A)
c) the inertia is changing. --> FALSE. The inertia of an object just depend on the mass and the velocity of the object: as neither the mass nor the velocity are changing in this problem, then the inertia of the car is not changing.
d) the forces of friction are proportional to the acceleration of the car. --> FALSE. Generally, the force of friction acting on an object moving on a flat surface is
where is the coefficient of friction, m is the mass, and g the acceleration of gravity. Therefore, the force of friction does not depend on the acceleration of the car.
e) All of the above. --> FALSE
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The gravitational force acting on the man is 800 N towards the Earth's centre
Explanation:
The weight of an object on the Earth is exactly the gravitational force exerted by the Earth on the object.
The gravitational force exerted by the Earth on an object located at the Earth's surface is given by:
where
G is the gravitational constant
M is the Earth's mass
m is the mass of the object
R is the radius of the Earth
And the direction of the force is towards the Earth's centre.
Since G, M and R are constant, they are grouped into a single constant called g, acceleration of gravity:
therefore the gravitational force can be rewritten as
And this is the usual equation that we use to calculate the weight of an object.
Therefore, weight and gravitational force acting on an object on Earth are the same thing: so, the gravitational force acting on the man is equal to his weight, 800 N, and it acts towards the Earth's center.
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