FORCES! Flashcards
What are Scalar quantities?
a scalar quantities have only magnitude (size) only and do not have direction.
What are vector quantities?
Vector quantities have magnitude and an associated direction.
How can vector quantities be represented?
With arrows.
What does the length of the arrow represent?
The length of
the arrow represents the magnitude
What does the direction of the arrow represent?
The direction of the vector quantity.
What is force?
A force is a push or pull that acts on an object due to the interaction with another object.
What are 2 things, forces have?
-Magnitude
-Direction
(Which means it a vector quantity)
What is the unit for force?
(N) newtons
What is contact force?
contact forces – the objects are physically touching
What is normal contact force?
When the 2 objects are in direct contact.
What is non-contact forces?
When the 2 objects are physically separated.
What are examples of contact force?
Examples of contact forces include:
-friction
-air resistance
-tension
-normal contact force.
What are examples of non-contact force?
Examples of non-contact forces are:
-gravitational force
-electrostatic force
-magnetic force.
What is gravity?
The force of attraction between all objects.
Is gravity a contact or non-contact force?
Non-contact force because the 2 objects are not physically touching.
Is gravity a vector quantity and if so why?
Yes. It is because it has both magnitude and direction.
What is the definition of mass?
The mass of an object tells us how much matter the object has in it.
What is the unit for mass?
Kg (Kilogram)
Is mass a scalar quantity and if so why?
Yes, it is a scalar quantity because it has no direction.
What is the definition of weight?
Weight is the force acting on an object due to gravity.
What is the unit for weight?
(N) Newtons
What is the formula for weight?
WMG
Weight (N) = Mass (Kg) x Gravitational field strength (N/Kg)
What is the gravitational field strength of Earth?
9.8N
TRUE OR FALSE:
The weight of an object is directly proportional to the mass of an object.
TRUE!
What is the symbol for directly proportional?
∝
What is the definition of the centre of mass?
The weight of an object may be considered to act at a single point referred to as the object’s ‘centre of mass’
What is the definition of a resultant force?
A number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together.
What is the formula for resultant force?
F resultant =F larger−F smaller
What is “work” ?
Work= When a force is used to move an object, energy is transferred
What is the formula for work done?
work done = force × distance
moved along the line of action of the force
W = F s
work done, W, in joules, J
force, F, in newtons, N
distance, s, in metres
When a force of 1N moves an object by 1m, then how much work is done?
When a force of 1N moves an object by 1m, then 1J of work is done
1 newton-metre of work…
1 newton-metre of work = 1 joule
What is the rule for distance for the formula of work done?
Distance must be in the line of action of the force.
What are elastic materials?
Elastic materials will always return to their original length or shape if we take away the forces acting on them.
What are inelastic materials?
a
When we stretch inelastic materials, they do not return to their original length when the forces are removed
How do we calculate the force needed to stretch an elastic object?
an elastic object?
a
force = spring constant × extension
F = k e
force, F, in newtons, N
spring constant, k, in newtons per metre, N/m
extension, e, in metres, m
What is inelastic deformation?
Once a material has gone past its elastic limit
What are we investigating in Required Practical 6: Stretching a Spring?
investigate the relationship between force and extension for a spring
What is the process of investigate the relationship between force and extension for a spring?
- Set up the apparatus: But a clamp stand with a heavy weight on it to stop it from falling. On the rod of the clamp stand put 2 bosses with 2 clamps. We attach a metre ruler vertically to one of the clamps and a spring (attached with a wooden splint horizontally as a pointer) on the other clamp. Ensure the top of the spring is at the zero point on the ruler
- Read the position of the ruler on the metre ruler (this is the unstretched length with no force attached)
- We then add a 1N weight on the spring and read the new position of the pointer on the metre ruler
- We repeat this continuing adding to add 1N weights to the spring and reading the position of the pointer
- We need to work out the extension produced by adding each weight. To do that we subtract the length of the unstretched spring from each reading
What is the relationship between the force and extension?
a linear relationship (directly proportional (straight line) )
What is inelastic deformation?
exceed the limit of proportionality
What is the formula for speed?
speed (m/s) = distance (m) / time (s)
SVT
DISTANCE-SPEED-TIME
What symbol is speed in the formula for speed?
V (m/s)
What symbol is distance in the formula for speed?
s (m)
What is the typical speed for a car on main road?
13 m/s
What is the typical speed for a fast train in UK?
50 m/s
What is the typical speed for a cruising aeroplane?
250 m/s
What is the typical speed of sound in the air?
330 m/s
What key point in the fact that the speed of sound can vary?
On warmer days sound travels faster compared to cooler days
What is the definition of velocity?
The velocity of an object is its speed in a given direction. Velocity is a vector quantity.
What happens when an object is moving at a constant speed in a circle?
then it’s velocity is constantly changing even though the speed is constant
What is the definition of acceleration?
The acceleration of an object tells us the change in it’s velocity over a given time.
What is the formula to find the acceleration at a constant speed?
v2-u2=2as
Final velocity (m/s) - initial velocity (m/s) = 2 x acceleration (m/s2) x distance (m)
When something falls to the surface of the earth how fast are they falling?
9.8 m/s
What is the definition of terminal velocity?
When the object stopped accelerating and moves at a constant velocity
What is Newton’s first law?
If the result force acting on a stationary object is zero then the object will remain stationary
If the resultant force acting on a moving object is zero then the object will continue moving in the same direction at the same speed . (save velocity.)
What is the definition of a resistance force?
When object is moving out of constant speed, there must be an equal force acting on the opposite side
What is Newton’s second law?
Acceleration of an object is proportional to the resultant force acting on it and is inversely proportional to the mass of the object
How do we calculate the force needed to accelerate an object?
Force = mass * acceleration
FMA
What is the definition of inertia?
An object for main stationary or constantly move at the same speed and direction unless a resultant force is applied.
What is the definition of inertia mass?
The inertia mass is a measure of how difficult it is to change the velocity of an object
What is Newton’s third law?
When two objects interact, the forces they exert on each other is equal and opposite
What is the method for required practical seven acceleration?
Steps:
1. Set up the apparatus: Place a trolley on a ramp, connected to a string that runs over a pulley with hanging masses at the other end.
2. Measure mass: Record the mass of the trolley and the hanging weights.
3. Mark starting point: Ensure the trolley starts from the same position each time.
4. Release the trolley: Let go of the trolley and allow it to accelerate as the hanging masses pull it forward.
5. Measure acceleration: Use light gates and a data logger to measure the acceleration of the trolley. Alternatively, use a stopwatch and measure the time taken to travel a known distance, then calculate acceleration using:
\text{Acceleration} = \frac{\text{Change in velocity}}{\text{Time taken}}
6. Repeat the experiment: Change the force by adding more masses to the string while keeping the trolley’s mass constant. Record the acceleration for each force applied. 7. Investigate mass variation (optional): Keep the force constant and change the mass of the trolley to see how it affects acceleration.
What should the student find out at the end of required practical seven?
What Should the Student Find Out?
• Acceleration increases as the force increases, confirming Newton’s Second Law:
F = ma
• Acceleration decreases when the mass of the trolley increases, if force is kept constant. • The results should show a direct proportionality between force and acceleration, meaning doubling the force should roughly double the acceleration.
What is the formula for kinetic energy?
Ek = 1/2 m v2
What is the key idea for momentum?
All moving objects have a momentum. But if an object is not moving, then the momentum is zero.
How do we calculate momentum?
Momentum (kg m/s) = mass (kg) x velocity (m/s)
