Shot oneShot two Shot Three What are the differences between these motions? What would happen if we continued firing the ball faster? What would change if the ball was fired from higher up? Projectiles – Vertical and Horizontal motion

In this demo we can see that the vertical and horizontal motions of the balls are independent. We can see this because both balls hit the floor at the same time regardless of how hard we hit the ball sideways!

This motion is normally described in an experiment called the monkey and the hunter. The monkey hanging in the tree hears a hunters gun and drops from the tree. The bullet however is pulled downwards with the same acceleration (gravity) and so they still meet!

In the picture below you can see the trace of the ball that is fired out of the “gun”. The other ball is just being dropped from the hand. Using the software – Multimedia motion you should be able to look at the velocity, displacement and acceleration of a single projectile and pairs of projectiles. In order to convince yourself of the fact that these two motions can be considered separate we should look at this simulation and how the horizontal and vertical motion are different. Also how the vertical motions of the two balls are actually very similar if not identical!

Answering Projectiles questions When trying to answer questions on projectiles there are a few things to remember before using the equations of uniform motion learned in section 1.1! positive direction 1)Define the positive direction for vertical motion Horizontal and Vertical motionNO EFFECT 2) Horizontal and Vertical motion have NO EFFECT on each other maximum heightvertical velocity is ZERO 3)At maximum height the vertical velocity is ZERO time takenmaximum heighthalf“flight” time ONLY transferable variable 4)The time taken to reach maximum height is half the total “flight” time and is the ONLY transferable variable between the two acceleration“flying”zero in the horizontal directionALWAYS DOWNWARDS “g” 5)The acceleration once the object starts “flying” is zero in the horizontal direction and the vertical acceleration is ALWAYS DOWNWARDS having a value of “g”

positive direction Horizontal and Vertical motion ARE separate maximum height vertical velocity is ZERO time taken to maximum height= half “flight” time time taken to maximum height = half “flight” time Acceleration is always downwards = “g”

a)State the direction of the acceleration of the ball during its flight b)Calculate the horizontal and vertical components of its velocity at A c)Calculate the maximum vertical height of the ball

(i)horizontal velocity component (2) (ii)vertical velocity component. (2) A second arrow is fired horizontally from the edge of a cliff 100 m high. a) Calculate the time for the arrow to hit the ground. (2) The arrow hits the ground a horizontal distance of 200 m from the edge of the cliff. b) Calculate the speed at which the arrow was fired. (2) An arrow is fired upwards at an angle of 45° to the horizontal. Describe and explain what happens during the flight to the

 Factsheet 63  Motion Support  S&C Projectile Motion