Forces Flashcards
What is the formula for average speed?
Average speed = distance / time
This can be represented as s = d / t.
What is the formula for acceleration?
Acceleration = change in velocity / time taken
This can be represented as a = (v-u) / t.
What defines a vector?
Vectors are physical quantities which have both a magnitude and direction
Examples include displacement, velocity, acceleration, force, and weight.
What defines a scalar?
Scalars are physical quantities with a magnitude, but not a direction
Examples include distance, speed, time, energy, and mass.
How is average speed typically measured?
Average speed is usually measured in m/s
Distance is measured in meters, and time in seconds.
What is the unit of measurement for distance?
Distance is measured in meters (m)
Ensure to convert units if necessary, e.g., km.
What is velocity?
Velocity is speed in a given direction
It is also measured in m/s.
Give an example where speed is constant but velocity changes.
An airplane doing a loop in the sky
The speed remains constant while the direction changes.
What is the relationship between change in velocity and acceleration?
Change in velocity is the final velocity minus the initial velocity
Acceleration is measured in m/s².
Fill in the blank: Average speed = _______
distance / time
Fill in the blank: Acceleration = _______
change in velocity / time taken
What does the gradient represent in a distance-time graph?
Velocity
A steeper gradient indicates a higher velocity.
What does a negative gradient in a distance-time graph indicate?
Returning back to the starting point
This means the object is moving in the opposite direction.
What does a horizontal line in a distance-time graph represent?
Stationary
The object is not moving during this time.
What does a curved line in a distance-time graph indicate?
Velocity is changing, and it is accelerating
This indicates that the object is speeding up or slowing down.
In a velocity-time graph, what does the gradient represent?
Acceleration
A steeper gradient indicates a higher acceleration.
What does a negative gradient in a velocity-time graph indicate?
Deceleration
This means the object is slowing down.
What does a horizontal line in a velocity-time graph represent?
Constant speed
The speed remains unchanged over time.
What does the area under the line in a velocity-time graph represent?
Distance travelled
This is calculated by multiplying speed and time.
What does a curved line in a velocity-time graph indicate?
Changing acceleration
The rate of acceleration is not constant.
In the investigation of toy cars, what was changed to measure speed?
The distance the cars were travelling down the ramp
This helps in observing the effect of distance on speed.
How was the speed of the toy cars measured during the experiment?
Using a light gate
The light gate triggers when the car passes through, providing a speed measurement.
Fill in the blank: In a distance-time graph, if the distance is zero, it means the object is _______.
Back at the starting point
This indicates no movement from the initial position.
What happens when the toy car passes the light gate?
The metal square triggers the light gate, and speed is recorded
This provides real-time speed data for the car’s motion.
What is the formula for force?
Force (N) = mass (kg) x acceleration (m/s²)
This is often represented as F = m x a.
What is the formula for weight?
Weight (N) = mass (kg) x gravitational field strength (10 m/s² on Earth)
This is often represented as W = m x g.
How is moment calculated?
Moment = force x perpendicular distance from the pivot (units are Nm)
Moment is a measure of the tendency of a force to rotate an object about an axis.
What type of quantity is force?
Force is a vector quantity
This means it has both magnitude and direction.
What effects can forces have on a body?
Forces can change the speed, shape, or direction of a body
They are measured in Newtons.
What are two examples of different types of forces?
- Gravitational
- Electrostatic
There are many other types of forces as well.
What does Newton’s first law state?
An object continues in a state of rest or uniform motion until acted on by a resultant force
This implies that an object will maintain its state unless influenced by an external force.
What happens to an object if it is moving according to Newton’s first law?
It will keep moving at the same speed in a straight line forever until acted on by a resultant force
This means no acceleration or deceleration occurs without a force.
What is the resultant force?
The overall force acted on an object by two or more forces acting along the same line
It determines the net effect of multiple forces.
How do you calculate the resultant force of two or more forces acting along the same line?
Add together the forces in the same direction and subtract the forces in the opposite direction
The resultant force acts in the direction of the larger number.
What is friction?
A force that opposes motion
Air resistance is a form of friction.
Fill in the blank: The formula for weight can be expressed as W = m x _______.
g
Where g is the gravitational field strength.
What is the resultant force when it is zero?
Object’s velocity stays the same - including stationary
A zero resultant force means no acceleration or change in motion.
What effect does a positive resultant force have on the motion of an object?
Object accelerates
A positive resultant force indicates a net force acting in the direction of motion.
What effect does a negative resultant force have on the motion of an object?
Object decelerates
A negative resultant force indicates a net force acting opposite to the direction of motion.
What comprises the total stopping distance of a car?
Thinking distance + braking distance
The stopping distance is the total distance required to bring a vehicle to a complete stop.
What factors can affect the thinking distance?
- Driver’s fatigue
- Alcohol consumption
- Drug influence
- Distraction
- Caffeine intake
- Greater speed
These factors can either increase or decrease the reaction time of the driver.
What factors can affect the braking distance?
- Greater speed
- Mass of vehicle and contents
- Poor road conditions
- Condition of the vehicle
These factors influence how quickly a vehicle can come to a halt once brakes are applied.
What happens to a falling object initially?
Faces no/little air resistance and accelerates downwards due to weight
The force of gravity acts on the object, causing it to fall.
What occurs as the downward velocity of a falling object increases?
Air resistance increases
This resistance eventually leads to terminal velocity where the object stops accelerating.
Fill in the blank: The total distance required to stop a car is equal to the sum of the _______ and the braking distance.
thinking distance
What is terminal velocity?
The point at which air resistance balances the object’s weight.
What happens to a skydiver as they fall?
They accelerate downwards until they reach terminal velocity.
What occurs when a skydiver opens their parachute?
Air resistance suddenly increases, resulting in a decrease of speed.
What happens to air resistance when the skydiver slows down after opening the parachute?
Air resistance decreases until it balances the skydiver’s weight.
What is a new lower terminal velocity in the context of skydiving?
The reduced terminal velocity that the skydiver reaches after opening the parachute.
Fill in the blank: Hooke’s law states that the extension of an object is proportional to the force - up to the _______.
elastic limit.
Define elastic behaviour.
The ability of a material to recover its original shape after the forces causing deformation have been removed.
What happens to elastic objects when the elastic limit is surpassed?
They are permanently deformed and the force is no longer proportional to the extension
Elastic objects return to their original shape up to their elastic limit.
How can you determine if values are directly proportional?
By plotting them on a graph; if the graph is a straight line through the origin, the values are directly proportional
After the elastic limit is reached, the graph becomes a curve.
Which materials obey Hooke’s law?
Springs and metal wires
Elastic bands do not obey Hooke’s law.
What is a moment in physics?
A measure of the turning effect of an object
Moments can be clockwise or anticlockwise as they are vector measurements.
What does the principle of moments state?
When an object is in equilibrium, the total clockwise moment equals the total anticlockwise moment.
Where does the weight of a body act?
Through its centre of gravity.
What condition must be met for a body to be stable?
Its centre of gravity must remain vertically above its base.
How do columns on a bridge work?
They share the weight of the object on the bridge. For example, if a 24,000 N object was in the middle of the bridge with two columns they would share 12,000 N each.
However, if it was 3/4 of the way across, the column it is closer to would experience 3/4 of the weight pushing upwards through it and the other column 1/4.
