General Science- Mechanics

Distance, Speed, Time (DVT)

Distance is a measure of how far away a point is. Measured in m/km

Speed is a measure of how fast an object is traveling. Measured in ms-1/kmh-1

Time is a measure of how long a period is taking. Measured in sec/hr

DVT Graphs- We can put information down into graphs that tell us a lot about how an object is moving.

The steeper the straight line the ‘higher’ the constant speed

The gradient of a straight line on a distance time graph gives the speed v=d/t OR v=rise/run

A ‘flat line’ means object is stopped/stationary

Curved line (upwards) acceleration away from the starting point

Curved line (downwards) deceleration/slowing down

Speed, Time graphs

A speed time graph that has a slope greater than zero shows an object accelerating

Graphs that show a straight line means a constant speed is being kept

Graphs that show a positive slop means the object is accelerating

Graphs that show a negative slope means the object is decelerating

The steeper the slope, the faster it is either accelerating or decelerating

Calculating Acceleration

To calculate the acceleration from a speed time graph you must calculate the slope the same way you would find the average speed distance time graph

Slope Y2-Y1= Y/X2-X1= X
Gradient= rise/run

Distance from area under graph

The total area under the slope represents the total distance

Area of a triangle= ½ x length x height
Area of square= length x height

Distance and Time- Revision

Motion is the way something is moving. The motion of an object such as a car/tennis ball is described using quantities like time, distance, speed and acceleration

Time (T), Seconds (S), Distance (D), Meters (M)

Speed

Average speed is a measure of distance traveled each hr/min/sec

Average speed= distance travelled/time taken

V= d/ t

Instantaneous speed- is the actual speed at any moment. The speedometer (speedo) in a car measures the instantaneous speed

Distance-Time graphs- Shows the time taken to travel a certain distance. The slope (gradient) of the graph gives info about the speed.

Slope (gradient)= change in y axis variable/ change in x axis variable

Slope= d/ t= Distance travelled/time taken

Acceleration- When a speed of an object changes, either by slowing down/ speeding up the object

Average acceleration- measures how much the speed is changing every hr/min/sec

Speed time graphs- give information about acceleration

The slope (gradient) of a graph of speed against time is found from slope= v/ t= change in speed/time taken= acceleration. The slope represents acceleration.

Force

A force can be defined as a push/pull/twist

Measured in newton’s (N)

A newton is equivalent to moving a 1kg mass, 1 metre

Force= mass x acceleration

N= kg x ms-2

Balanced and Unbalanced forces

Balanced Forces
Equal forces acting on one object in opposite directions

Acceleration is zero

Speed is constant

Net forces= 0 (no charge in motion)

Drawing forces on a diagram

Force, Mass, Acceleration

The heavier the object, the more force that is required to accelerate you

Acceleration-Gravity-10ms-2

Mass vs. Weight

Mass- amount of matter in a object measured in kilograms (kg)

Weight- measure of the force on an object due to acceleration caused by gravity measured in newtons (N)

Friction

Friction happens when an object moves against another. Friction always acts to oppose (or stop) the movement of an object. Types of friction include drag and air resistance. Friction generates heat, ‘causes wear and tear and slows moving