At what angle should an arrow with an initial speed of 45m/s be aimed so that it will hit an apple 25m away on the same horizontal line?

Write the equation for the horizontal position of the arrow as a function of time and its initial velocity and angle, and set it equal to 25 m.. Then write out the equation for vertical motion, also as a function of time and initial velocity and angle, and set it to 0. Now you have two equations in two unknowns (time and angle); solve for the angle.

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Originally Posted by ebaines

Write the equation for the horizontal position of the arrow as a function of time and its initial velocity and angle, and set it equal to 25 m.. Then write out the equation for vertical motion, also as a function of time and initial velocity and angle, and set it to 0. Now you have two equations in two unknowns (time and angle); solve for the angle.

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sorry I don't get what you are saying. Please can you write down an example equation as a function of time. I really appreciate your kind help.

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Originally Posted by teveleng

sorry I don't get what you are saying. Please can you write down an example equation as a function of time. I really appreciate your kind help.

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If a projectile is launched at angle from the horizontal with initial velocity , the component of its horizontal velocity is , and its horizontal position as a function of time is:

.

It's initial vertical velocity is , and its vertical position as a function of time is:

.

I trust these equations are not unfamiliar to you.