P2.2 - Forces Flashcards
What is the unit of force?
The unit of force is a Newton.
What can forces do?
Force can change the shape of an object or change its motion or its state of rest.
When two objects interact what can we say about the forces acting?
They always exert equal and opposite forces on each other.
What is the resultant force?
A single force that the same affect as all the forces acting on an object.
What happens to an object if it’s resultant force is zero?
The object stays at a constant velocity.
How is resultant force calculated?
- The sum of the forces in the same direction.
- The difference of the forces in opposite directions.
How does the acceleration of an object depend on the size of the resultant force?
The bigger the resultant force, the greater the acceleration.
What effect does the mass of an object have on its acceleration?
The greater the mass, the smaller the acceleration for a given force.
How is resultant force on an object calculated from its mass and acceleration?
Resultant force (N) = mass (kg) x acceleration (ms^1) F=ma
Which forces oppose the driving force of a car?
Friction and air resistance.
Give the two factors which affect stopping distance.
Thinking and braking distance.
Give four factors that can increase the braking distance.
- Poor weather (ice, rain etc.)
- High speed.
- Poor brakes.
- Poor tyres.
Give two factors which can effect thinking distance.
- Poor reaction time (caused by phone, alcohol, drugs etc.)
- High speed.
How is the braking force required effected by the car?
The greater the speed, the more deceleration needed to stop the object.
The greater the mass, the greater the braking force needed.
What is the difference between mass and weight?
The weight of an object is the force of gravity on it.
The mass of an object is the quantity of matter in it.
What is the motion of a falling object only effected by gravity?
The object accelerates at 10ms^-2.
What is terminal velocity?
The maximum velocity an object reaches when falling in a fluid.
The weight is equal to the drag force.
How is weight calculated?
weight (N) = mass (kg) x gravitational field strength (Nkg^-1)
W=mg
How is the extension of an object measured?
The difference between the length and the original length.
How does the extension of a spring vary with the force applied?
The extension of the spring is directly proportional to the force up to the point of proportionality.
What is the spring constant of a spring?
The force per unit extension needed to stretch it.
What force is stored when an elastic object is stretched?
Elastic Potential Energy
What is the equation of Hooke’s Law?
force applied (N) = spring constant (Nm^-1) x extension (m) F=ke
Give four ways the fuel economy of vehicles be improved.
- Reducing the speed.
- Fitting a wind deflector (for lorries.)
- Fully inflating the tyres.
- Removing excess weight.
What is an average speed camera?
Linked pairs of cameras which record the vehicle’s average speed.
How do anti-skid surfaces work?
The rougher surface increases friction meaning more force can be applied before the brakes lock.
