Motion and Forces Flashcards
Explain the term scalar quantity and give examples
A quantity with just a magnitude
Examples: speed, distance, mass, energy, time
Explain the term vector quantity and give examples
A quantity with magnitude and a direction.
Examples: velocity, displacement, force, momentum, acceleration
What is velocity?
Speed with a stated direction.
What are some important factors to distance/time graphs? (5)
- Gradient is velocity
- Sharper gradient means faster speed.
- Horizontal lines means stationary.
- Area under line = nothing.
- Curved line means that the velocity is changing.
What are some important factors to velocity/time graphs? (5)
- Gradient is acceleration.
- Sharper gradient means acceleration.
- Horizontal lines constant speed.
- Area under line = distance travelled
- Curved line means that the acceleration is changing
How to use light gates to determine the speed? (4)
- Set up two light gates, one at the start and one at the end.
- Measure distance between them.
- As soon as the object passes through the first gate, it will measure the time taken to reach the second light gate.
- Then use speed=distance/time. This method is more accurate as it removes reaction time and human error with a stopwatch.
Recall typical speeds:
wind
sound
walking
running
cycling
bus
train
plane
wind: 5-7ms^-1
sound: 340ms^-1
walking: 5km/h = ~1.4ms^-1
running: ~6 miles per hour = ~3ms^-1
cycling: 15km/hh = ~4ms^-1
bus: 14km/h
train: 125miles/h
plane: 900km/h
What is newtons first law?
An object has a constant velocity unless acted on by a resultant force.
Recall newtons first law and what happens when the resultant force is zero (2)
- No acceleration
- So moving at a constant velocity or the object is at rest.
Recall newtons first law and what happens when the resultant force is not zero (2)
- Acceleration is change in velocity over time.
- So the velocity will change and the direction or speed of the object will change (or both).
CORE PRACTICAL - Investigate the relationship between force,
mass and acceleration by varying the masses added to trolleys (6)
- Start by measuring the mass of the trolley using a balance.
- Begin the experiment with only the trolley, no added masses and record its initial velocity as it passes through the light gates.
- Add 0.1kg mass increments to the trolley, repeating the velocity measurements at each step.
- Record the time taken for the trolley to pass through the light gates and its velocity each time.
- Calculate the acceleration using the equation acceleration = change in velocity/time.
- Plot a graph of acceleration against mass, which should exhibit a smooth curve indicating acceleration and mass are inversely proportional. Plot a graph of acceleration against the inverse of mass, which should yield a straight line, confirming that acceleration and mass is inversely proportional.
What is inertial mass?
This is a measure of how difficult it is to change the velocity of an object.
Inertial mass = force/acceleration
What is Newtons Third Law?
Every action force has an equal and opposite reaction force.
What is momentum?
Momentum is always conserved in a collision (where there are no external forces like friction, air resistance, electrostatic attraction).
What is the Ruler Drop Experiment? (4)
- Someone else holds a ruler just above your open hand.
- They drop it at a random time.
- Record the distance from the bottom of the ruler to the point where it was caught.
- Average these values.
