A –Level Physics: Kinematics- Projectiles

Objectives: Additional skills gained: Advanced calculation Spec point 9: be able to use the equations for uniformly accelerated motion in one dimension using SUVAT equations Spec point 15: understand how to make use of the independence of vertical and horizontal motion of a projectile moving freely under gravity Additional skills gained: Advanced calculation Component Isolation

Lesson-Link: Hunter and Monkey Quandary B C A hunter has a tranquiliser dart and wants to hit the monkey. The moment she shoots the arrow, the monkey spots her and drops down. Should she aim A) above the monkey B) at the monkey or C) below the monkey?

Lesson-Link: Hunter and Monkey: The hunter (or rather the arrow) Let’s consider the path of the arrow if she shoots directly at the monkey. What dimensions is it travelling in? Horizontal Ignoring the horizontal movement, if I were to take pictures of the arrow’s vertical position every half a second or so, what would that look like? Vertical

Lesson-Link: Hunter and Monkey: The hunter (or rather the arrow) When we looked at forces, what did we learn about horizontal and vertical components? They can be isolated as the quantities that act vertically do not affect those acting horizontally and vice versa. Constant Velocity (e.g. 60ms-1) Ignoring the horizontal movement, if I were to take pictures of the arrow’s vertical position every half a second or so, what would that look like? Uniform Acceleration ( 9.81ms-2)

Lesson-Link: Hunter and Monkey: And the monkey? Well the monkey is only moving in one dimension. And this is the same as the vertical component as the arrow! Ignoring the horizontal movement, if I were to take pictures of the arrow’s vertical position every half a second or so, what would that look like? The horizontal component of the arrow is irrelevant! It will still accelerate due to gravity vertically just as the monkey will! Uniform Acceleration ( 9.81ms-2)

Real life context: Strobe drops! Increasing distance (accelerating!) Set distance Horizontally (constant speed!)

Using SUVAT to solve projectile problems: Condition 1: Horizontal Throws A man cliff-dives off the edge of a 60m tall cliff horizontally with a velocity of 8.2ms-1 . How long is he in flight and what horizontal distance does he cover? Horizontal component: 6. We now know that time= 3.5s As the velocity horizontally has to be constant, we can use v=s/t, rearrange for s (displacement) s= v x t s= 8.2ms-1 x 3.5 S= 28.7m Vertical Component: 2. Needed: t Have: s, u, a 3. Only one we can use is 𝐬=𝐮𝐭+ 𝟏 𝟐 𝐚𝐭𝟐 U=0ms-1, a=9.81ms-2, s=60m 4. Well as u is 0, we can get rid of ‘ut’. We’re left with 𝟏 𝟐 𝐚𝐭𝟐 Rearrange= t= 𝟐𝒔/𝒂 5. Therefore time= 𝟐×𝟔𝟎 𝟗.𝟖𝟏 = 3.5s! Work on the vertical component first Identify known values Identify equation that can be used Must have the mystery value Has no other unknown values Rearrange the equation Solve for vertical component value Use the value of time to work out the horizontal component using v= s/t

Hint: work out time first Practice Questions The hunter is stood on a 30m tall hill facing a monkey at the same height in a tree (parallel). She shoots a dart horizontally causing the monkey to drop. The dart hits the monkey 6m above the ground, how far away is the hunter from the monkey? Hint: work out time first A student throws his rucksack horizontally out of a window that is 18m above the ground with a velocity of 3.1ms-1, how far away must his friend stand in order to catch it?

Using SUVAT to solve projectile problems: Condition 1: Throws at an angle To the sports hall! Force for one = cos 35 x 6500 = 5324. Both = 10648N. A= F/m = 10.6ms-2

I/S over the autumn holiday Write a 1500-2000 word essay to explain how Newtonian physics and Kinematic Equations can be used in real life situations. Include examples of calculations undertaken (feel free to research values) and diagrams. Force for one = cos 35 x 6500 = 5324. Both = 10648N. A= F/m = 10.6ms-2

Objectives: Additional skills gained: Advanced calculation Spec point 9: be able to use the equations for uniformly accelerated motion in one dimension using SUVAT equations Spec point 15: understand how to make use of the independence of vertical and horizontal motion of a projectile moving freely under gravity Additional skills gained: Advanced calculation Component Isolation