In a ‘soapbox’ competition a driver raced against the clock in a straight line down a track in a vehicle with no power source - Junior Cycle Science - Question c - 2016

From the graph, to find the time taken to reach 80 m, identify the time value when the distance is 80 m. This occurs at approximately 18 seconds. Thus, the time taken for the vehicle to travel 80 m is:

Time = 18 s ± 0.5 s

To calculate the average speed during the last four seconds (from 16 s to 20 s):

1. Determine the distance travelled during this period:

   • Distance at 16 s = 44 m
   • Distance at 20 s = 100 m
   • Distance travelled = 100 m - 44 m = 56 m

2. The time taken is 4 seconds.

3. Average speed can be calculated using the formula:

   ext{Average Speed} = rac{ ext{Distance}}{ ext{Time}} = rac{56 ext{ m}}{4 ext{ s}} = 14 ext{ m/s}

Thus, the average speed is 14 m/s.

Speed and velocity are both measures of how fast an object moves, but they have distinct differences:

1. Direction: Speed is a scalar quantity, which means it only has magnitude (how fast something is moving). Velocity is a vector quantity, which includes both speed and direction (where something is moving).

2. Displacement: Velocity is defined as displacement over time, while speed is the distance travelled over time.

3. Magnitude: Speed is the absolute measure of how fast an object is moving, irrespective of its direction, while velocity takes into account the specific direction of motion.

In summary, speed is how fast you are going, while velocity is how fast you are going in a certain direction.