suppose a car manufacturer tested its cars for front end collsion by hauling them up on a crane and dropping them from a certain
1 answer:
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:
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Answer:
The kinetic energy of the phone would increase. The gravitational potential energy of the phone would decrease.
Explanation:
The kinetic energy of an object is proportional to the square of the speed of that object. If air resistance is negligible, the phone would accelerate under gravitational pull and speed up. Hence, the kinetic energy of the phone would increase.
The gravitational field near the surface of the earth is approximately constant. Hence, the gravitational potential energy of the phone would be proportional to its height. As the phone approaches the ground, the height of the phone becomes lower and the gravitational potential energy of the phone would decrease.
Answer:
No, it is not conserved
Explanation:
Let's calculate the total kinetic energy before the collision and compare it with the total kinetic energy after the collision.
The total kinetic energy before the collision is:
where m1 = m2 = 1 kg are the masses of the two carts, v1=2 m/s is the speed of the first cart, and where v2=0 is the speed of the second cart, which is zero because it is stationary.
After the collision, the two carts stick together with same speed v=1 m/s; their total kinetic energy is
So, we see that the kinetic energy was not conserved, because the initial kinetic energy was 2 J while the final kinetic energy is 1 J. This means that this is an inelastic collision, in which only the total momentum is conserved. This loss of kinetic energy does not violate the law of conservation of energy: in fact, the energy lost has simply been converted into another form of energy, such as heat, during the collision.