Answer:
b. Friction decreased when he went from pavement to ice and then increased two more times.
Explanation:
Frictional force depends on the normal force of the surface and a friction coefficient.
Since we're talking about the same car, the value of will remain constant whereas μ will represent the change in the frictional coefficient of the surface. Now we consider the different surfaces, cars will slide in an icy road which means that the frictional coefficient is smaller than the pavement.
After Joshua returns to the pavement road, the resulting frictional force increases and will do so one more time when he reaches the gravel road. Gravel roads have greater frictional coefficients than pavement roads which means the frictional force will increase a second time.
Answer:
The distance is 55.636 billion miles, or 528.2 AU.
Explanation:
Since the distance from the Sun to Neptune is 2.7818 billion miles, the distance from the Sun to Planet Nine would be 20 times that, which is:
or 55.636 billion miles.
Since 1 astronomical unit (AU) is 93 million miles, that distance is also:
Initial height: 66.5 m
Explanation:
The problem can be solved by using the principle of conservation of energy.
If we neglect air resistance, the total mechanical energy of the car is conserved during the fall, therefore we can write:
where :
is the kinetic energy of the car at the top (it starts from rest)
is the gravitational potential energy of the car at the top, with:
m = the mass of the car
g = the acceleration of gravity
h = the heigth of the car
is the kinetic energy of the car just before hitting the ground, with
v = 130 km/h final speed of the car
is the gravitational potential energy of the car at the bottom
Re-arranging the equation, we find
and we have:
Solving for h, we find the initial height of the car:
Learn more about kinetic energy and potential energy:
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