Motion and Forces Flashcards
What are vectors?
Quantities that have both size (or magnitude) and (specific) direction, such as force, weight, acceleration, displacement, momentum, etc
What are scalars?
Quantities that do not have specific direction but do have size (magnitude), such as distance, energy, time, speed, mass and temperature
What is velocity?
Speed in a set direction
What is displacement?
Distance travelled in a straight line (distance covered)
What is acceleration?
How fast velocity changes
How do you calculate speed?
Distance/Time
What do the following mean in a Distance/Time graph: -Gradient -Straight increasing line -Flat sections -Steeper graph -Curves -Curve getting steeper -Levelling off/decreasing gradient ?
- Speed
- Steady/Constant speed
- Where it has stopped
- Going faster
- Acceleration
- Speeding up
- Slowing down
What is a tangent?
A line that is parallel to the curve at that point
How do you calculate the gradient of a line?
Change in the vertical/Change in the horizontal (Rise/Run)
How do you calculate the average speed on a Distance/Time graph?
Total distance travelled/Time taken to travel total distance
What do the following mean in a Velocity/Time graph: -Gradient -Flat sections -Steep slope -Uphill slope Downhill slope -Curve -Straight line up or down
- Acceleration
- Steady speeds
- The greater the acceleration/deceleration
- Acceleration
- Deceleration
- Changing acceleration
- Constant acceleration/deceleration
What is the area of the ‘inside’ of the graph equal to?
The distance travelled in that time interval
How do you calculate acceleration?
Final velocity-Starting velocity/Time
What are the units for acceleration?
M/s squared
When can you only use a tangent?
On a curve
How do you calculate final velocity?
Rearrange equation of
V squared - U squared = 2 X acceleration X distance
How do you calculate force?
Acceleration X Mass
Why do you transfer masses during the trolley experiment?
To keep the mass of the whole system 9trolly and mass of hook) the same
What safety precaution should you take for the trolley experiment?
Stay standing so you can move away quickly in case the trolley or weights fall, or use a newspaper-filled box to land
Why should the trolley hold a piece of card with a gap in the middle?
It will interrupt the beam of light from the two light gates (twice) and send this data to the data logger/computer that it is connected to
How does the data logger calculate the acceleration of the trolley?
By doing Speed = Distance/Time to get the velocity from each light gate and then putting it into the acceleration equation to get the acceleration between the two light gates of the trolley
How do you calculate weight/force (newtons)?
Mass (kg) X Gravitational Field Strength (N/kg)
What does Newton’s first law state?
A resultant force is needed to make something start moving, speed up or slow down
What will a non-zero resultant force always produce?
Acceleration or deceleration in the direction of the force
What is the relationship between force and acceleration?
Directly proportional
What is the formula that describes Newton’s First Law?
Resultant Force (N) = Mass (KG) X Acceleration (M/S squared)
What is intertial mass?
A measure of how difficult it is to change the velocity of an object
What is inertia?
The tendency to continue moving at the same velocity (constant)
How do you calculate inertial mass?
Inertial mass (KG) = Force (N)/Acceleration (M/S squared)
How does the acceleration due to gravity practical work?
After entering the length of the card into the datalogger, the card will be able to work out the velocity using the that length and the time from which the beam of light (invisible to us) has been broken; it will break twice as there are 2 light gates
What is the difference between mass and weight?
Mass is the amount of stuff you’re made up of and weight is the effect of gravity on mass
What is the typical speed for: -Walking -Running -Cycling -Driving -(Gale force) Wind -Sound in air -Light ?
- 1.5 m/s
- 3.0 m/s
- 6.0 m/s
- 14 m/s
- 16 m/s
- 330 m/s
- 300 million /ms
What does Newton’s first law state?
A body will remain at rest/continue in a straight line at a constant speed as long as the forces acting on it are balanced
What does Newton’s second law state?
When a resultant force acts on a mass then there will be a change in its velocity
What is the centre of gravity?
The point from which the whole weight of an object appears to act
What does gravitational field strength depend on?
- Mass of the body
- Radius of the body
How do you calculate weight?
Weight (N) = Mass (KG) X Gravitational field strength (N/KG)
What is the value for gravitational field strength for the following astronomical bodies:
- Earth
- Moon
- Neutron star
- 9.8 N/KG
- 1.6 N/KG
- 10^12 N/KG
What is the relationship between terminal velocity and weight?
Directly proportional
What is terminal velocity affected by?
Shape and size
What is centripetal force?
A force that acts in a curve; forces you into a circular motion. The acceleration is towards the centre of the circle
What happens at terminal velocity?
The air resistance force and weight are equal so the speed is constant
What are the 4 main types of centripetal force that will result in circular motion?
- Gravitational
- Frictional
- Tension
- Electrostatic
What is the formula for gravitational field strength using time and height?
2h/t^2
height in metres, time in seconds
How do you calculate momentum (KG M/S)
Momentum (KG M/S) = Mass (KG) X Velocity (M/S)
P = M X V
How do you calculate force from momentum and time?
Force (N) = Change in momentum (KG M/S)/ Time taken for the change (S)
F = m(v-u)/t
What do car safety features do to limit the size of forces on the driver/passengers?
(Such as seat belts and crumple zones) They limit the time over which the vehicle comes to rest because they are inversely proportional
How is force related to momentum?
Force is the rate of change of momentum
What angles must centripetal forces work at?
Right angles to the direction of motion and towards the centre of the circle
What is the relationship between distance and gravitational force?
Inversely proportional
What happens in terms of momentum when objects interact?
Momentum can be transferred between the objects and so total momentum stays the same
What does Newton’s third law state?
Whenever two objects interact, they exert equal and opposite forces on each other; for every action, there is an equal and opposite reaction
What does it mean when momentum is conserved?
The total momentum before the collision equals the total momentum after the collision
What is the equation for Newton’s second law?
F = A X M
What is the formula for kinetic energy?
1/2 X Mass X Velocity^2
What is the formula for work done?
Force X Distance moved in the direction
What is the formula for stopping distance?
Stopping distance = Thinking distance/Braking distance
Thinking distance = distance car travels while the driver reacts to danger and applies brakes
Breaking distance = distance car travels while it’s slowing down once the brakes have been applied
