Which of the following is a phase change?
1 answer:
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a) The work done by the tree is
b) The amount of force applied is 2880 N
Explanation:
a)
According to the work-energy theorem, the work done on the car is equal to the change in kinetic energy of the car. Therefore, we can write:
where
W is the work done on the car
m is the mass of the car
u is its initial speed
v is its final speed
For the car in this problem, we have:
m = 2000 kg
u = 12.0 m/s
v = 0 (since the car comes to a stop, after the crash)
Therefore, the work done by the tree on the car is:
The work is negative because it is done in the direction opposite to the direction of motion of the car.
b)
The work done by the tree on the car can also be rewritten as
where
F is the force applied on the car
d is the displacement of the car during the collision
In this situation, we have:
is the work done
is the displacement of the car during the collision
Solving the equation for F, we find the force exerted by the tree on the car:
Where the negative sign means the force is applied opposite to the direction of motion of the car. Therefore, the magnitude of the force applied is 2880 N.
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We have . So,
.
. So
.
Thus we can convert the units of the given quantity.
That is,
.
The quantity is converted to the required units.