Speed, Velocity and Acceleration Relationships

March 10th 2010

• What is Speed?

Speed is basically the measurement of an object's motion whether it is accelerating or decelerating and is usually measured in m/s. Speed is found when dividing the covered distance and the amount of time taken to cover it. E.G. The athlete sprinted the 100m race and finished in 10 sec, therefore his speed is:

100 m ÷ 10 sec

= 10m/s

• What is Acceleration and Deceleration?

Acceleration is when an object is starts to speed up. E.g. A skydiver falling would accelerate or generate speed as he/she is falling. Deceleration however, is when an object slows down. E.G. If a skydiver deploys his/her parachute, it will create air resistance causing him/her to slow down or decelerate.

• What is Velocity?

Velocity however, is also the measurement of an object's motion as well as its direction and displacement. Velocity tells us the speed of the object as the direction in which it is going E.G. If a car moves in reverse and covers 70 m in 1 second, the average speed would be 70m/s while the average velocity would be - 70m/s. This is because the car is going in the oppisite direction and therefore has a negative velocity. The speed remains the same since speed is only the measure of how fast or slow an object's motion is and disregards direction.

• What is Terminal Velocity?

Terminal Velocity is basically when an object reaches at a stable and balanced velocity. Take a skydiver for example, he/she will continue accelerating due to the force of gravity that is acting on him/her. The acceleration will come to an end after air resistance starts to increase and balances out the gravitational forces. When that balance had been made then the person would have reached terminal velocity.

• Is there any difference between Speed and Velocity?

Of course there is, but it is not clear or visible. Speed is measuring only how fast or slow an object's motion is, while velocity measures that and the direction of that motion. Look and compare these two graphs:

Graph A:

Graph B:

These two graphs are both a speed graph and a velocity graph respectively. As you can see the difference between these graphs is that one graph measures just the speed of the object and the other measures the speed and direction. One evidence is that in the velocity graph, the velocity goes under zero. This means that the object is going in the opposite direction.

The Speed and Weight on Moon

March 7th 2010

How did I calculate my walking and running speed?

I calculated my walking and running speeds similarly. First, I set up 2 cones at a distance of 10m from each other. Next, I walked the distance while being timed and did the same for running. My running and walking times were then put on the Distance, Speed and Time triangle:

• Walking:

Speed

= Distance÷Time

= 10 m ÷ 5.5 sec

= 1.8 m/s

• Distance:

Speed

= Distance÷Time

= 10 m ÷ 2.47 sec

= 4.1 m/s

Why are our weights different on other planets?

This is because your weight depends on the mass of the planet, the distance you are from the center of the planet and the amount of force that is applied on you while you are on the planet. E.g. On earth, you are applied with 10N of force while on the moon you are only applied with 1.6N of force, therefore your weight decreases while on the moon.