Physics · Motion and force. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Distance is the length of the path travelled. Displacement is the straight-line change of position from start to finish, with a direction. Speed uses distance; velocity uses displacement. Average velocity covers a whole time interval, while instantaneous velocity is the value at one moment, found as the interval is made very small.
Acceleration is the rate of change of velocity. On a velocity-time graph the gradient gives the acceleration and the area under the graph gives the distance covered. On a displacement-time graph the gradient gives the velocity.
When the acceleration is uniform, three equations link the five quantities. A body in free fall has a = g = 9.8 m s−2 downwards.
Students mix up the signs in vertical motion. Choose one direction as positive at the start and give every velocity, displacement and acceleration a sign that fits it.
Answer: 25 m s−1, reached after 20 s
Type what you are stuck on. The helper finds the explanation, worked examples and the notes to read, free and instant.
← Torque and equilibriumNewton's laws, momentum and collisions →Take a Physics test