Speed and Force (Key Stage 2 level 6)
Speed
Speed is considered to be the rate at which an object covers a particular distance. An object moving at great speed is said to cover a considerable distance in a short period of time. On the other hand, an object moving at low speed covers a relatively smaller distance during the same span of time. Therefore, the distance covered over a period of time is proportional to the speed of the particular object and conversely if there is no movement then the speed is considered to be zero.
Acceleration
Acceleration is often used in an inappropriate sense when it is related to going fast or at a great pace. In fact, going fast bears no relation to acceleration. An object can move at an immense speed but that does not necessarily mean it is accelerating. The change in the velocity of an object is acceleration. Therefore, if there is no change in the velocity of an object then acceleration is considered to be zero. At any point of movement if there is a change in the velocity of an object then at that point of time the object is said to be accelerating.
This can be further explained by taking an object which moves between three points named A, B and C. If the object is at rest at point A and then force is applied which causes it to move at a velocity of 10 m/s from point A to point B then the acceleration is said to be 10 m/s. Again if the force is increased on the object causing it to move at a velocity of 25 m/s from point B to point C then the acceleration is said to be 15 m/s which is the change or increase in speed of the object. It must however be kept in mind that in this example the object was assumed to be at rest before it was acted upon by force and that is why acceleration was caused in its initial movement from point A to point B.
Constant acceleration
When objects change their velocity by the same amount then there is constant acceleration. Again taking the example of three points and assuming the object to be at rest at point A, if the object moves from point A to point B at 10 m/s and then from point B to point C at 20 m/s then in both cases the change or increase in velocity is 10 m/s. This is referred to as constant acceleration.
Note: Acceleration should not always be taken to be a consequence of the increase in the velocity of an object. When an object is slowing down, the acceleration is said to be in the direction opposite to that of its motion. This is referred to as the Rule of the Thumb.
Force
In scientific terms, force is an agency or action that causes a body of mass to accelerate. There are different kinds of forces such as gravitational force, electromagnetic force, and centrifugal force.