Forces Flashcards
Explain the difference between scalar and vector quantities and contact and non contact forces
Vector quantities have a magnitude and direction, scalar quantities only have magnitude
When two objects have to be touching for a force to act, the force is a contact force, if the objects do not need to be touching it is a non contact force
What is the formula for calculating the weight of an object
Weight(N)=Mass(kg) x gravitation field strength (N/kg)
What is a free body diagram
A free body diagram shows all the forces acting on an object by using arrows to show the direction and relative magnitudes of the forces.
Give the formula for calculating the work done by a force and explain what each symbol means
Work done (J)=Force(N) x Distance(M)
How many joules of work does one Nm equal
1 Joule
Describe the forces acting on an object in equilibrium
All the forces are balanced to give a resultant force of 0
What is the difference between an elastic and an inelastic deformation?
An elastic deformation will return back to it’s original shape, an inelastic deformation won’t
Give the equation that relates force, extension and the spring constant of an object
Force(N)=Spring constant(N/m) x extension (m)
What is the limit of proportionality
The maximum force above which the graph curves showing extension is no longer proportional to the force
How do you find the following from a linear force-extension graph: spring constant and work done
The gradient of the line is equal to the spring constant.
The energy in the elastic potential store is equal to the area under the force extension graph up to the limit of proportionality
Give the equation used to find the energy in an elastic object’s elastic potential energy store
Elastic potential energy (J)=1/2 x spring constant(N/m) x Extension^2(m)
Define a moment and state an equation for calculating the size of a moment
A moment is the turning effect of a force.
Moment(Nm)=Force(N) x distance from pivot(m)
If a seesaw is balanced what can you say about it’s components
The anti clockwise moment is equal to the clockwise moment
State an equation for calculating the pressure at the surface of a fluid.
Pressure(Pa)=Force(N)/Area of surface(m^2)
Explain why the pressure increases as you go deeper into a column of a liquid
As the depth of the liquid increases, the number of particles above that point increases. The weight of these particles adds to the pressure felt at that point.
What causes an object to float
When an object is submerged in a fluid pressure is exerted wth a resultant force upwards known as upthrust. The upthrust is equal to the weight of fluid that has been displaced. If an object’s weight is equal to the upthrust the force balance and the object floats.
Explain how and why atmospheric pressure varies with height
As the altitude increases the atmosphere gets less dense so there are fewer air molecules that are able to collide with the surface. There are also fewer air molecules above a surface meaning the weight of the air above it decreases.
What is the difference between displacement and distance
Distance is a scalar quantity so doesnt involve direction. Displacement is a vector quantity measuring distance and direction in a straight line form an object
Define acceleration in terms of velocity and time
Acceleration is the change in velocity in a certain amount of time
What does the term uniform acceleration mean
Uniform acceleration means a constant acceleration
What does the gradient represent for a distance time graph and a velocity time graph
The gradient in a distance time graph means speed. The gradient in a velocity time graph means acceleration
What is terminal velocity and what causes it
Terminal velocity is the maximum speed an object can reach at a steady speed. At first speed is much higher than drag but as speed increases (acceleration) drag increases until the forces are balanced and the object travels at a constant speed.
State Newton’s three laws of motion
Newtons first law:A resultant force is needed to make something start moving, speed up or slow down
Newtons second law:A force to be equal to change in momentum per change in time. Force and the acceleration are directly proportional and acceleration is inversely proportional to the mass of an object.
Newtons third law:When two objects interact the forces they exert on each other are equal and opposite.
What is inertia
Until acted upon by a resultant force, objects at rest stay at rest and objects moving at a steady speed will stay moving at that speed.
