Assuming the ball's initial velocity was 57° above the horizontal and ignoring air resistance, what did the initial speed of the
ball need to be to produce such a home run if the ball was hit at a point 0.9 m (3.0 ft) above ground level?
Assume that the ground was perfectly flat. Express your answer using two significant figures. v₀ = ______ m/s
How far would the ball be above a fence 3.0 m (10 ft) high if the fence was 116 m (380 ft) from home plate? Express your answer using two significant figures. h = _______ m
Assume that the ground was perfectly flat. Express your answer using two significant figures. v₀ = ______ m/s
How far would the ball be above a fence 3.0 m (10 ft) high if the fence was 116 m (380 ft) from home plate? Express your answer using two significant figures. h = _______ m
1 answer:
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1) The initial momentum of the trophy is zero
2) The initial momentum of the bowling ball is 160 kg m/s
3) The total momentum before the collision is 160 kg m/s
4) The total momentum of the system after the collision is 160 kg m/s
5) The final velocity of the trophy is 32 m/s
Explanation:
1)
The momentum of an object is given by
where
m is the mass of the object
v is its velocity
In this problem, the data for the trophy before the collision are:
m = 2 kg is the mass
v = 0 is its initial velocity
Therefore, the initial momentum of the trophy is
2)
Using the same equation used in part 1), the initial momentum of the bowling ball is
where
m is the mass of the bowling ball
v is its initial velocity
The data of the problem are
m = 8 kg is the mass
v = 20 m/s is the velocity
Substituting,
3)
The total momentum of the system before the collision is given by the sum between the initial momentum of the trophy and the initial momentum of the bowling ball:
where
is the initial momentum of the trophy
is the initial momentum of the ball
Here we have
Therefore, the total momentum is
4)
According to the law of conservation of momentum, for an isolated system (=no external unbalanced forces acting on the system), the total momentum of the system is conserved before and after the collision:
where
is the total momentum before the collision
is the total momentum after the collision
If we consider the system in the problem to be isolated (i.e. no frictional forces acting on the ball or the trophy), we can therefore say that the total momentum after the collision must be equal to the total momentum before the collision: therefore,
5)
We can write the total momentum after the collision as
where:
is the mass of the trophy
is the final velocity of the trophy
is the mass of the bowling ball
is the final velocity of the ball
Since we also know the value of the final total momentum,
we can solve the equation to find the velocity of the trophy:
Learn more about momentum:
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Answer:
a) v=2.743m/s
b)
c) T=2.543N
Explanation:
First, calculate the height of the ball at the starting point:
At this point, just in the moment the ball is released, all the energy of the system is potencial gravitational energy. When it is at the bottom all the potencial energy is transformed into kinetic energy:
Solving for v:
if h is the height loss: (l-y')
v=2.743m/s
The centripetal acceleration is the acceleration caused by the tension force exercised by the string, and is pointing outside of the trayectory path (at the lowest point, directly dawn):
To calculate tension, just make the free body diagram of forces in the ball, noticing the existence of the centripetal acceleration: