Example: Finding the range of a projectile

In the previous example of time of flight, the out of control bus is forced to jump from a location 0,40,5m with an initial velocity of 80,7,5m/s1. We have now found the time of flight to be 3.65s and now want to find the position of where the bus returns to the ground.

Facts

Lacking

Approximations & Assumptions

Representations

Diagram of forces acting on bus once it leaves the road.

bus_abstract.jpg

The general equation for calculating the final position of an object:

rf=ri+vavgΔt

Also know as the position update formula.

Solution

From the previous problem you already know the final location of the ball in the y direction to be 0 as it has met the ground after 9.59s.

We now to find the range in the x and z directions in order to have a position vector for the final resting place of the bus.

There is no force acting in the x or z directions as the only force acting on the system is the gravitational force which acts in the y-direction.

This means that the initial velocities in both of these directions have remained unchanged.

We know the amount of time the bus has been traveling in the x-direction at its initial velocity and its initial position so we can compute the distance travelled in this direction using the position update formula for x-components.

xf=xi+Vavg,xΔt

Plug in respective values for variables.

=0+80m/s(3.65s)

Compute range in x-direction.

=292m

Repeat same process for the z-components:

zf=zi+Vavg,zΔt

Plug in respective values for variables.

=5+5m/s(3.65s)

Compute range in z-direction.

=23.25m

Write range(final position vector) using all components:

Final position = 292,0,23.255m