A placekicker kicks a football upward at an angle of 30 and a speed of 5.0 m/s at what other angle will he have to kick a second ball with the same speed to reach the same distance downrange ignore air resistance

60

90

45

15

Respuesta :

Answer:[tex]60^{\circ}[/tex]

Explanation:

Given

speed of ball [tex]u=5 m/s[/tex]

launch angle [tex]\theta =30^{\circ}[/tex]

Range of a Projectile [tex]R=\frac{u^2\sin 2\theta }{g}[/tex]

Range will be common for two angles i.e. [tex]\theta [tex] and [tex]90-\theta [/tex]

for [tex]\theta R=\frac{5^2\sin 2\cdot 30}{g}[/tex]

[tex]R=2.209 m[/tex]

For [tex]90-\theta [/tex]

[tex]90-30=60^{\circ}[/tex]

[tex]R=\frac{5^2\sin 2\cdot 60}{g}[/tex]

[tex]R=2.209 m[/tex]

Answer:

The other angle is 60°

(a) is correct option.

Explanation:

Given that,

Angle = 30

Speed = 5.0 m/s

We need to calculate the range

Using formula of range

[tex]R=\dfrac{v^2\sin(2\theta)}{g}[/tex]...(I)

The range for other angle is

[tex]R=\dfrac{v^2\sin(2(\alpha-\theta))}{g}[/tex]...(II)

Here, distance and speed are same

From equation (I) and (II)

[tex]\dfrac{v^2\sin(2\theta)}{g}=\dfrac{v^2\sin(2(\alpha-\theta))}{g}[/tex]

[tex]\sin(2\theta)=\sin(2(\alpha-\theta))[/tex]

Put the value into the formula

[tex]\sin(2\times30)=\sin(2\times(\alpha-\theta))[/tex]

[tex]\sin60=\sin2(\alpha-30)[/tex]

[tex]60=2\alpha-60[/tex]

[tex]\alpha=\dfrac{60+60}{2}[/tex]

[tex]\alpha=60^{\circ}[/tex]

Hence, The other angle is 60°.