Answer :
1) Initial speed: 10.0 m/s
2) Angle of projection: [tex]78.5^{\circ}[/tex]
3) Velocity of the ball 0.100 s before being caught: [tex](v_x,v_y)=(2.00,-8.82) m/s[/tex]
4) Position of the ball 0.100 s before being caught: [tex](x,y)=(3.79, 0.93+h)m[/tex] (where h is the height of the man)
Explanation:
1-2)
The motion of the ball is a projectile motion, so it consists of two independent motions:
- A uniform motion (constant velocity) on the x-axis
- A uniformly accelerated motion (constant acceleration) on the y-axis
In this part, we analyze only the vertical motion, which can be described by the suvat equation:
[tex]s=u_y t - \frac{1}{2}gt^2[/tex]
where
s is the vertical displacement
[tex]u_y = v_0 sin \theta[/tex] is the initial vertical velocity, with [tex]v_0[/tex] being the initial speed and [tex]\theta[/tex] the angle of projection
[tex]g=9.8 m/s^2[/tex] is the acceleration of gravity
t is the time
The ball reaches the ground again when the displacement is zero, s = 0, so we have
[tex]0=v_0 sin \theta t - \frac{1}{2}gt^2[/tex]
So, neglecting the solution for t =0,
[tex]v_0 sin \theta = \frac{1}{2}gt[/tex] (1)
where t = 2.00 s is the time of flight.
At the same time, the third baseman runs backwars at velocity
v = 7.00 m/s
From an initial distance of
L = 18.0 m
So his x-position at time t is
[tex]x_b(t) = L-vt[/tex]
While the x-position of the ball at time t is
[tex]x_s(t)=u_x t = v_0 cos \theta t[/tex]
The player catches the ball when the two positions are the same:
[tex]L-vt=v_0 cos \theta t[/tex] (2)
Dividing eq.(1) by eq.(2) we get
[tex]\frac{tan \theta}{t}=\frac{gt}{2(L-vt)}[/tex]
And so we can use this to find the angle of projection:
[tex]\theta = tan^{-1}(\frac{gt^2}{2(L-vt)})=tan^{-1}(\frac{(9.8)(2.00)^2}{2(18-(7)(2))})=78.5^{\circ}[/tex]
And now we can use eq.(2) to find the initial speed of the ball:
[tex]v_0=\frac{L-vt}{cos \theta t}=\frac{18-(7)(2)}{cos 78.5^{\circ} \cdot 2.00}=10.0 m/s[/tex]
3)
Here we want the velocity of the softball 0.100 s before the ball is caught, so at time
t = 2.00 - 0.100 = 1.90 s
The components of the velocity of the softball are given by:
[tex]v_x = v_0 cos \theta[/tex] which is constant, therefore
[tex]v_x = (10.0)(cos 78.5^{\circ})=2.00 m/s[/tex]
While the y-component of the velocity is given by the equation for accelerated motion:
[tex]v_y = v_0 sin \theta -gt[/tex]
And substituting t = 1.90 s,
[tex]v_y = (10.0)(sin 78.5^{\circ})-(9.80)(1.90)=-8.82 m/s[/tex]
where the negative sign indicates that the direction is downward.
Therefore the vector expression for the velocity of the ball at 0.100 s before it has been caught is
[tex](v_x,v_y)=(2.00,-8.82) m/s[/tex]
4)
The x-position of the ball at time t is given by the equation for uniform motion:
[tex]x=v_0 cos \theta t[/tex]
And substituting t = 1.90 s,
[tex]x=(10.0)(cos 78.5)(1.90)=3.79 m[/tex]
Instead, the vertical position of the ball is given by the equation of uniformly accelerated motion:
[tex]y=v_0 sin \theta t - \frac{1}{2}gt^2[/tex]
And substtuting t = 1.90 s, we find
[tex]y=(10.0)(sin 78.5^{\circ})(1.90)-\frac{1}{2}(9.80)(1.90)^2=0.93 m[/tex]
Of course we have measured the vertical displacement from the head of the player who hit the ball; therefore, we have to add his height, h. So the position of the ball at t = 1.90 s is
[tex](x,y)=(3.79, 0.93+h)m[/tex]
Learn more about projectile motion:
brainly.com/question/8751410
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