# Fence Height for Detached Race Car Wheel at 45m/s

• chrisridgwell
In summary: Once you have the length of each side you can use basic trigonometry to solve for the angle. In this case, the angle is 35 degrees and the length of the hypotenuse is 9.8 meters, so the height of the fence must be 9.8 meters to prevent the wheel from hitting the crowd.
chrisridgwell
a wheel becomes detached from a race car, the wheel is traveling at 45m/s at an angle of 35 deg. a fence is erected 25m from the track. ignoring air resistance how high should the fence be?

gravity 9.8

ive tried drawing a diagram, with angle of 35 deg. i believe it is a trig question

see that doesn't make any sense to me!

What will be the vertical and horizontal components of velocity using trig?

see that's where I am stuck i need to know how to calculate this:
if i know the angle and the adjacent,
35 deg, 25m and i want to the height, opposite, 35 x 25 as in Tan x adj

Ahh I see. You misunderstand slightly, its not assimple as that. The wheel does not travel in a straight line since it is subject to gravity and that is why you need to use kinematic equations. You use trig to find the components of the velocity vector (i.e. the magnitude of the velocity is the hypotenuse of a right angled triangle). The components tell you the horizontal and vertical velocity of the wheel to which you can apply the kinematic equations.

i was lead to believe it would travel in a straight line as its traveling at 45m/s and the fence is only 25m away

chrisridgwell said:
i was lead to believe it would travel in a straight line as its traveling at 45m/s and the fence is only 25m away

By who? If that is the case why were you given the gravitational acceleration of g?

sorry if i have confused it, this is an assignment question which i got late as i missed a lesson
the question says that the wheel is traveling at 45m/s at 35 deg. the fence is 25m away, how high does it have to be to prevent it hitting the crowd. then in brackets it just says take gravitational field strength to be 9.8 N/kg

The you will definitely need to take gravity into account. So begin by finding the components of the wheels velocity and then use the appropriate kinematic equations to see how high the wheel will be when it reaches the fence.

what do you mean by components? I am sorry I am new to physics

Like I said previously consider the vector as the hypotenuse of a right angled triangle. The other two sides of the triangle will then be the components of the vector which you can work out using trigonometry. Read the following page for more information on vectors in general including resolving components.

http://hyperphysics.phy-astr.gsu.edu/hbase/vect.html

im stuck now, as the horizontal is flat so it is at 0 degress, and i can't calculate the other side as i don't have the information to.

Both sides can be calculated from the hypotenuse and the angle. Did you read the link I gave you about resolving components? Its just the same as calculating the length of sides of a right-angled triangle in trigonometry class.

## 1. What is the recommended fence height for a detached race car wheel traveling at 45m/s?

The recommended fence height for a detached race car wheel traveling at 45m/s is at least 6 feet (1.8 meters). This height is based on safety standards and regulations set by racing organizations to prevent debris and accidents from reaching spectators.

## 2. How does the speed of the race car affect the recommended fence height?

The speed of the race car directly affects the recommended fence height. As the speed increases, the height of the fence should also increase to ensure the safety of spectators. The higher the speed, the taller the fence should be to prevent debris from flying over and potentially causing harm.

## 3. Are there any other factors besides speed that determine the recommended fence height?

Yes, in addition to speed, other factors such as the size and weight of the detached race car wheel, the angle of impact, and the type of track surface can also influence the recommended fence height. It is important to consider all of these factors when determining the appropriate fence height.

## 4. Can a lower fence height be used if the race track has protective barriers in place?

No, even if the race track has protective barriers in place, the recommended fence height for a detached race car wheel traveling at 45m/s should still be at least 6 feet (1.8 meters). This is because the protective barriers may not be able to fully contain the detached wheel, and a taller fence can provide an extra layer of protection.

## 5. Is the recommended fence height the same for all types of racing events?

No, the recommended fence height may vary depending on the type of racing event. For example, for open-wheel racing events, a higher fence height may be required due to the potential for cars to become airborne. It is important to follow the specific guidelines and regulations for each type of racing event to ensure the safety of both participants and spectators.

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