P9: Motion

What is the difference between distance and displacement?

• Distance is a scalar quantity measuring how far an object has moved along a path.

• Displacement is a vector quantity measuring the straight line distance and direction from start to finish.

What is the difference between speed and velocity?

• Speed is a scalar quantity measuring how fast an object moves regardless of direction.

• Velocity is a vector quantity measuring speed in a given specified direction.

What are the typical speed values for human movement, transport, and sound?

• Walking speed is 1.5 meters per second, running is 3 meters per second, and cycling is 6 meters per second.

• Cars travel at 13 to 30 meters per second, trains at 50 meters per second, and passenger planes at 250 meters per second.

• Sound travels through air at approximately 330 meters per second.

How do you determine speed and motion features from a distance-time graph?

• The gradient or slope of the line equals the speed of the object.

• A flat horizontal line indicates the object is stationary.

• A straight sloping line indicates constant speed, while a curved line indicates changing speed or acceleration.

How do you calculate speed at a specific time on a curved distance-time graph?

Draw a tangent line touching the curve at that specific time point and calculate the gradient of the straight tangent line.

What is acceleration and how is it defined?

The rate of change of velocity per unit time, measured in meters per second squared.

What is the value of acceleration for an object falling freely near Earths surface?

Approximately 9.8 meters per second squared due to gravity.

How do you determine acceleration and motion features from a velocity-time graph?

• The gradient or slope of the line equals the acceleration of the object.

• A flat horizontal line indicates the object is moving at a constant velocity.

• A line sloping upwards shows positive acceleration, while a line sloping downwards shows deceleration.

How do you find the total distance travelled from a velocity-time graph?

Calculate the total area underneath the graph line, splitting the area into simple geometric shapes such as rectangles and triangles.

How does an object in freefall achieve terminal velocity?

• Gravity initially accelerates the object downwards because weight is much greater than air resistance.

• As speed increases, air resistance increases, which reduces the resultant downward force and acceleration.

• Eventually air resistance increases to equal weight, making resultant force zero so the object falls at constant terminal velocity.