Question

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

Answer 1

Answer:$60^{\circ}$

Explanation:

Given

speed of ball $u=5 m/s$

launch angle $\theta =30^{\circ}$

Range of a Projectile $R=\frac{u^2\sin 2\theta }{g}$

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

for $\theta R=\frac{5^2\sin 2\cdot 30}{g}$

$R=2.209 m$

For $90-\theta$

$90-30=60^{\circ}$

$R=\frac{5^2\sin 2\cdot 60}{g}$

$R=2.209 m$

Answer 2

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

$R=\dfrac{v^2\sin(2\theta)}{g}$...(I)

The range for other angle is

$R=\dfrac{v^2\sin(2(\alpha-\theta))}{g}$...(II)

Here, distance and speed are same

From equation (I) and (II)

$\dfrac{v^2\sin(2\theta)}{g}=\dfrac{v^2\sin(2(\alpha-\theta))}{g}$

$\sin(2\theta)=\sin(2(\alpha-\theta))$

Put the value into the formula

$\sin(2\times30)=\sin(2\times(\alpha-\theta))$

$\sin60=\sin2(\alpha-30)$

$60=2\alpha-60$

$\alpha=\dfrac{60+60}{2}$

$\alpha=60^{\circ}$

Hence, The other angle is 60°.