Forces Flashcards
When two objects interact what can be said about the forces exerted on each other?
They are equal and opposite.
What is resultant force?
When a number of forces acting at a point may be replaced by a single force that has the same affect as motion as the original forces.
A resultant force may cause an object to what?
Change in its state of rest or motion.
If the resultant force acting on a stationary object is zero, the object will…
…remain stationary.
If the resultant force acting on a stationary object is not zero, the object will…
…accelerate in the direction of the resultant force.
If the resultant force acting on a moving object is zero, the object will…
…continue to move at the same velocity.
If the resultant force acting on a moving object is not zero, the object will…
…accelerate in the direction of the resultant force.
Equation for acceleration (force).
F = ma or a = F/m
Where:
F is force (N)
m is mass (kg)
a is acceleration (m/s^2)
Velocity is…
…the speed of an object with direction.
Acceleration equation (velocities).
a = (v-u)/t
Where: a is acceleration (m/s^2) v is final velocity (m/s) u is initial velocity (m/s) t is time (s)
Gradient of distance/time graphs represents what?
Speed.
Gradient on velocity/time graphs represents what?
Acceleration.
When a vehicle travels at a steady speed, what can be said about the resistive forces and the driving forces?
They are balanced (no resultant force).
The greater the speed of a vehicle the greater the what is needed to stop it in a certain distance?
Braking force.
The stopping distance of a vehicle is a sum of what?
The driver’s thinking distance plus the braking distance.
A driver’s reaction time can be affected by what?
Tiredness, drugs and alcohol.
When the brakes of a vehicle are applied what happens?
Work done by the friction force between the brakes and the wheel reduce the kinetic energy of the vehicle and the temperature of the brakes increases.
Braking distance can be affected by what factors?
Adverse road or weather conditions and poor condition of the vehicle (brakes or tyres).
The faster an object moves through a fluid the greater the…
…frictional force acting on the object.
An object falling through a fluid will initially…
…accelerate due to the force of gravity.
Eventually the resultant force of an object falling through a fluid will reach…
…zero and the object will be moving at its terminal velocity (steady speed).
Weight of an object equation:
W = mg
Where:
W is weight (N)
m is mass (kg)
g is gravitational field strength (N/kg)
A force acting on an object may cause it to what?
Change shape.
When a force is applied to an elastic object, such as a spring, the object will…
…stretch and stored elastic potential energy.
For an object that is able to recover its shape, what happens (elasticity)?
Elastic potential energy is stored in the object when work is done on the object to change its shape.
The extension of and elastic object is directly proportional to what?
The force applied, provided that the limit of proportionality is not exceeded for the object.
What is the formula for extension of an elastic object?
F = ke
Where:
F is force (N)
k is the spring extension (N/m)
e is the extension (m)
