# Determining the speed of a rocket car

• Solidearth
In summary, the conversation discusses a science club's special event for homecoming, where a rocket is attached to a decorated car and provides constant acceleration for 9 seconds before a parachute opens and slows the car at a rate of 5m/s^2. The car reaches the judges' box in the center of the grandstand, 990m from the starting line, exactly 12 seconds after the rocket is fired. The use of kinematics equations is suggested to solve for the unknown variables and determine the location of the car at all times. The only unknown variable is the acceleration while the rocket burns, which can be found by setting the acceleration equal to a and solving for a when x=990m
Solidearth

## Homework Statement

Your school science club has devised a special event for homecoming. You've attached a rocket to the rear of a small car that has been decorated in the blue-and-gold school colors. The rocket provides a constant acceleration for 9s. As the rocket shuts off, a parachute opens and slows the car at a rate of 5m/s^2. The car passes the judges' box in the center of the grandstand, 990m from the starting line, exactly 12s after you fire the rocket.

## Homework Equations

Kinematics equations

## The Attempt at a Solution

by splitting the car's motion into two segments (car+rocket, and car+parachute) the motion is easier to discuss.
car+rocket
vo=0m/s
to=0s
tf=9.0s
xo=0m
xf=unknown
a=unknown
vfrocket=unknown

car+parachute
vo=unknown
vf=unknown
xo=xfrocket
xfchute=990m
achute=-5.0m/s2
ti=9s
tf=12s

okay but now what, there are too many unknown variables, where would i even start?

The only unknown is the acceleration while the rocket burns. Once you know that, you know the initial location and velocity, and the acceleration at all times, so you should be able to determine the location of the car for every t.

Just set this acceleration equal to a, and find out what a must be to make x = 990 as t = 12

## 1. How do you calculate the speed of a rocket car?

In order to calculate the speed of a rocket car, you need to know the distance traveled and the time it took to travel that distance. The formula for speed is speed = distance/time. So if the rocket car traveled 100 meters in 5 seconds, the speed would be 20 meters per second.

## 2. What equipment is needed to determine the speed of a rocket car?

To determine the speed of a rocket car, you will need a measuring device such as a stopwatch or a timer, a distance measuring tool such as a measuring tape, and a rocket car capable of recording its own speed.

## 3. Can the speed of a rocket car change during its journey?

Yes, the speed of a rocket car can change during its journey. It can accelerate, decelerate, or maintain a constant speed depending on the force applied to it.

## 4. How does air resistance affect the speed of a rocket car?

Air resistance can affect the speed of a rocket car by creating drag, which slows down the car's movement. The more streamlined the car is, the less air resistance it will face and the faster it can go.

## 5. Is there a maximum speed a rocket car can reach?

There is no specific maximum speed for a rocket car, as it depends on various factors such as the car's design, the amount of fuel it has, and the surface it is traveling on. However, rocket cars have been known to reach speeds of over 700 miles per hour.

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