Which object would have the most kinetic energy?
2 answers:
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Average force on the window: 0.32 N
Explanation:
The average force exerted on the window is given by Newton's second law
where
is the net change in momentum of the hailstones in a time interval of
In order to find the change in momentum, we have to consider only the component of the hailstone's momentum perpendicular to the window, therefore:
is the initial momentum of one hailstone, with
m = 7 g = 0.007 kg is the mass
is the initial speed
is the angle with the window
The final momentum is
where
v = 4.5 m/s is the final speed (the collision is elastic so the speed is equal, while the direction changes)
(after the rebound, the direction has changed)
So the change in momentum of 1 hailstone is
We are interested only in the magnitude, so
There are 595 hailstones hitting the window in 49 s, so the total change in momentum is
And therefore, the average force on the window is
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Answer:
The final velocity of the car A is -1.053 m/s.
Explanation:
For an elastic collision both the kinetic energy and the momentum of the system are conserved.
Let us call
= mass of car A;
= the initial velocity of car A;
= the final velocity of car A;
and
= mass of car B;
= the initial velocity of car B;
= the final velocity of car B.
Then, the law of conservation of momentum demands that
And the conservation of kinetic energy says that
These two equations are solved for final velocities and
to give
by putting in the numerical values of the variables we get
and
Thus, the final velocity of the car A is -1.053 m/s and of car B is 3.49 m/s.