physics-motion

physics-motion

1. distance time graphs

   • we can use graphs to help us describe the motion of an object
   • a distance time graph shows the distance of a object from a starting point against the time taken
   • the speed of a object is the distance traveled each second
   • the gradient on a distance-time graph shows the speed. the steeper the gradient the greater the speed
   • if a object is stationary the line on the distance will be horizontal
   • if an object is moving at a constant speed the line on the distance-time graph will be represented as a strait line that slopes upwards
   • we can calculate the speed of an object by using a simple equation
     • speedm/s=distance traveled in metres/ time taken in seconds
   • distance-time graphs are to do with speed NOT acceleration

2. more about velocity time graphs

   • a velocity time graph shows the velocity of an object against the time taken
   • the gradient of the line on a velocity time graph represents acceleration
   • the steeper the gradient the greater the acceleration
   • if the line on a velocity time graph is horizontal, the acceleration is zero. therefore the object is moving at a constant speed
   • if the gradient on the line is negative then the object is decelerating
   • velocity-time graphs are to do with acceleration NOT speed

3. velocity and acceleration

   • the velocity of an object is its speed in a given direction
   • if an object changes direction it changes velocity, even if its speed stays the same
   • if the velocity of an object changes we say that its accelerating
   • we can calculate acceleration by using the equation:
     • a=v-u/t
   • if the value for accelerationis negative, the object is decelerating (slowing down). deceleration is the same as negative acceleration
   • where: A is the acceleration in m/s ^2, V is the final velocity m/s , U is the initial velocity m/s and T is the time taken s

4. using graphs

   • if you calculate the gradient of the line on a distance time graph you answer will be the speed of the object
   • if you calculate the gradient of the line on a velocity time graph your answer will be the acceleration of the object
   • calculating the area under the line between two times on a velocity time graph gives the distance travelled between those times