Chapter 2 - Forces Flashcards
What are action and reaction forces
When an object exerts a force on another object and that objects exerts an equal and opposite force back on that object
What is the resultant force
The single force that has the same effect as all the forces acting on an object
What are forces measured in
Newtons
When the resultant force on an object is zero, what happens when
•An object is at rest
•An object is moving
If an object is at rest, it will stay at rest
If an object is moving, it will carry on moving at the same speed and in the same direction
What is the equation to find the resultant force on an object
F= m x a
F = Resultant force (N) M= Mass (Kg) A= Acceleration (m/s2)
Why might the force needed to give an object a particular acceleration have to be bigger
If the mass of an object is bigger
Why might the resultant force on an object be zero it was travelling at a steady speed
The driving forces are equal and opposite to the friction forces
How is the thinking distance increased
- If the driver is tired
* If the driver is under the influence of alcohol or drugs
How is the braking distance increased
- Poorly maintained roads
- Bad weather conditions
- Condition of the car (worn tyres, worn brakes)
What is a drag force
The force exerted on an object when it falls through a fluid. The faster the object falls, the bigger the drag force until eventually it will be equal to the weight of the object
What is fuel economy
Reducing the speed of a vehicle which reduces the amount of fuel it uses to travel a particular distance
What do anti skid surfaces do
Increase the friction between a car tyre and the road surface
What does a resultant force always cause
Acceleration
What is a negative acceleration
Deceleration
What is needed to make an object change direction
A resultant force
Why might the force needed to give an object a particular acceleration have to be bigger
If the mass of an object is bigger
Why might the resultant force on an object be zero it was travelling at a steady speed
The driving forces are equal and opposite to the friction forces
What is the stopping distance
The distance a vehicle travels during the thinking distance plus the braking distance
How is the thinking distance increased
- If the driver is tired
* If the driver is under the influence of alcohol or drugs
How is the braking distance increased
- Poorly maintained roads
- Bad weather conditions
- Condition of the car (worn tyres, worn brakes)
What is a drag force
The force exerted on an object when it falls through a fluid. The faster the object falls, the bigger the drag force until eventually it will be equal to the weight of the object
What is terminal velocity
The velocity an object reaches when it’s falling in a liquid. The weight is then equal to the drag force on the object
What does the term extension mean
The difference between the length of the spring and its original length
What is an elastic object
An object that regains its original shape when the forces deforming it are removed
What is Hooke’s law
The extension is directly proportional to the force applied, provided the limit of proportionality is not exceeded
What is the equation for Hooke’s law
F= k x e
F= Force applied (N) K= Spring constant (the force per unit extension needed to stretch it) in N/m E= extension (m)
What is fuel economy
Reducing the speed of a vehicle which reduces the amount of fuel it uses to travel a particular distance
Give another example of improving fuel economy
Reducing the air resistance by making the vehicle more streamlined
Why does skidding happen
When the brakes on a vehicle are applied too harshly. The wheels lock and slide along the road surface increasing the stopping distance
