Robbie Knievel ride On May 20,1999, Robbie Knievel easily cleared a narrow part of the Grand Can

step 1 Okay, so question 21. Robbie Knievel ride. Robby Knievel Ride on May the 20th, 1999. Robbie Knie

Robbie Knievel ride On May 20,1999, Robbie Knievel easily...

Key Concepts

Projectile Motion

Projectile motion describes the motion of an object that is launched into the air and is only subject to the acceleration due to gravity. The object moves along a parabolic path because its horizontal velocity remains constant (if air resistance is neglected) while its vertical velocity is influenced by gravity.

Decomposition of Velocity

In projectile motion, the initial velocity is typically split into horizontal and vertical components using trigonometric functions based on the launch angle. This decomposition is essential for analyzing how far and how high the projectile will travel because it separates the motion into two independent directions.

Application of Kinematic Equations

Kinematic equations relate displacement, initial velocity, time, acceleration, and final velocity. In projectile problems, these equations are used separately for the horizontal component (where acceleration is zero) and the vertical component (where acceleration is equal to the gravitational acceleration), allowing for the calculation of unknown quantities such as the launch speed.

Assumptions in Projectile Motion

Common assumptions include neglecting air resistance, assuming the gravitational acceleration is constant, and considering level ground or a consistent reference point for the motion. These assumptions simplify the problem by allowing the use of basic kinematic equations without additional complicating factors.

Transcript

00:01 Okay, so question 21.

00:04 Robbie knievel ride.

00:06 Robby knievel ride on may the 20th, 1999.

00:11 Robbie knievel easily cleared a narrow part of the grand canyon during a world -record setting, long -distance motorcycle jump, 69 .5 metres.

00:26 He left the jump ramp at a 10 -degree angle above the horizontal.

00:30 How fast was he travelling when he left the ramp? indicate any assumptions you made.

00:38 Okay, so, well, there's an awful lot going on here.

00:42 There is some gap that has to be traversed.

00:47 And at the same time, we are leaving with a velocity, an initial velocity, we'll just mark that as u, the letter u, with 10 degrees to the horizontal as i launch.

01:06 Velocity.

01:08 Okay, and so first of all we've definitely got two directions in which everything acts.

01:15 The horizontal and the vertical directions and we're literally saying that y is the vertical and x is the horizontal.

01:28 And so it's worth doing what i usually do, which is to note a few interesting characteristics across everything.

01:39 And call these suvatt equations.

01:41 If you're familiar with them or if you're not, basically s is the distance in which you go.

01:47 U is your initial velocity in that direction.

01:51 V is your final velocity in that direction.

01:54 A is your acceleration and t is time and these are all interlinked.

02:02 So we know that we travel at 69 .5 for 69 .5 meters if we're at robbie knievel.

02:11 And we've got some velocity that we don't know, u -0, let's call it u -0 in the x direction, but of course it's not just in the x direction, it's new not cosign of 10 degrees in the x direction.

02:29 And of course our final velocity is likewise equal to u -0 cosine of 10 degrees in the x direction because we are ignoring air resistance, so there is no change in acceleration.

02:42 And time? well, we'll just call that time.

02:48 We're just trying to get an establishment of what we know.

02:53 So to clear our gap, we're assuming no change in height.

02:57 Ideally, we should not go negative.

03:00 And in the limit of the equation, we should not go below zero.

03:05 So our height starts at zero, it ends at zero, and it does not go below zero.

03:12 Our initial velocity, therefore, is equal to u -0, sign of 10.

03:17 10 degrees.

03:22 And here's where we get a little clever.

03:25 Because our final velocity in our direction at the very limit, well our path is going to be a symmetric one.

03:37 And so if we were travelling at u0, sine 10 upwards, when we took off, we should be travelling at negative u0, sign 10 degrees when we land.

03:53 We'll see if this helps us later.