Galileo, in his book Two new sciences, stated that “for elevations which exceed or fall short of $45^o$ by equal amounts, the ranges are equal”. Prove this statement.
Answer For a projectile launched with velocity
$v _{ o }$ at an angle $\theta_{ o },$ the range is given by
$R=\frac{v_{o}^{2} \sin 2 \theta_{0}}{g}$
Now, for angles, $\left(45^{\circ}+\alpha\right)$ and $\left(45^{\circ}-\alpha\right), 2 \theta_{0}$ is $\left(90^{\circ}+2 \alpha\right)$ and $\left(90^{\circ}-2 \alpha\right),$ respectively. The values of $\sin \left(90^{\circ}+2 \alpha\right)$ and $\sin \left(90^{\circ}-2 \alpha\right)$ are
the same, equal to that of $\cos 2 \alpha .$ Therefore, ranges are equal for elevations which exceed or fall short of $45^{\circ}$ by equal amounts $\alpha$
A fighter plane is flying horizontally at a height of $250\ m$ from ground with constant velocity of $500\ m/s$. It passes exactly over a cannon which can fire a shell at any time in any direction with a speed of $100\ m/s$. Find the duration of time for which the plane is in danger of being hit by a cannon shell
A player kicks a football with an initial speed of $25\, {ms}^{-1}$ at an angle of $45^{\circ}$ from the ground. What are the maximum height and the time taken by the football to reach at the highest point during motion ? (Take g $=10 \,{ms}^{-2}$ )
Two projectiles are thrown simultaneously in the same plane from the same point. If their velocities are $v_1$ and $v_2$ at angles $\theta _1$ and $\theta_2$ respectively from the horizontal, then answer the following question
If $v_1\,\,cos\,\,\theta _1 = v_2\,\,cos\,\,\theta _2$, then choose the incorrect statement
A projectile is thrown upward with a velocity $v_0$ at an angle $\alpha$ to the horizontal. The change in velocity of the projectile when it strikes the same horizontal plane is
Given below are two statements. One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion A :Two identical balls $A$ and $B$ thrown with same velocity '$u$ ' at two different angles with horizontal attained the same range $R$. If $A$ and $B$ reached the maximum height $h_{1}$ and $h_{2}$ respectively, then $R =4 \sqrt{ h _{1} h _{2}}$
Reason R: Product of said heights.
$h _{1} h _{2}=\left(\frac{u^{2} \sin ^{2} \theta}{2 g }\right) \cdot\left(\frac{u^{2} \cos ^{2} \theta}{2 g }\right)$
Choose the $CORRECT$ answer