Hints for projectiles calculations
Projectiles can be fairly challenging calculations due to the combination of resolving vectors and use of equations of motion under gravity. It's important to show working clearly and bear the following in mind:
- At each stage consider which component you are working with. Don't mix up vertical and horizontal values.
- Time is the only variable common to both components.
- Write down the known and unknown variables at each stage for that component.
- From rest means \(u=o\).
- Be careful to consider + or 鈥 with each velocity or displacementQuantity describing the distance from the start of the journey to the end in a straight line with a described direction, eg 50 km due north of the original position.. (up is positive).
- Acceleration due to gravity on Earth is -9.8 ms-2 and the negative must be included in calculations.
- If a projectile is moving horizontally the vertical velocityThe speed of an object in a particular direction. is 0.
- If a projectile takes off and lands on a level surface, the final vertical velocity is equal and opposite to the initial velocity upwards.
- To calculate the resultantThe combination of two or more vectors. For example, the resultant of a 30 N force up and a 40 N force horizontally is 50 N at 37掳 above the horizontal.. velocity at any time, both vertical and horizontal components must be added in a vector triangle.
- Always state a direction if an answer asks for a velocity, eg 7.2 ms-1 at 30掳 below the horizontal.
Question
Which component affects the time the projectile spends in the air?
The vertical component.
The horizontal component has no effect on the time of flight.