7B Forces Flashcards
What are the three visible effects of a force?
Push, pull or twist
Give three examples of contact forces.
Friction, air resistance, drag, reaction force and upthrust
Give three examples of non-contact forces.
Gravity, magnetism and electrostatic attraction
What is the difference between a contact and non-contact force?
Contact forces require objects to be touching, non-contact forces do not
How can forces affect an object’s speed?
Slow it down or speed it up
Why are forces measured in Newtons?
Isaac Newton described the laws of gravity
What effect will balanced forces have on a car travelling at a constant speed on 70mph?
Continue at same speed in same direction
What effect will unbalanced forces have on a tennis ball resting on a table?
Start to move
What does the length of a force arrow tell us on a force diagram?
The size of a force
How can we tell in what direction the force is acting on a force diagram?
The direction the arrow is pointing
How would we draw a pair of balanced forces acting on an object?
Equal sized arrows
Define resultant force
A single force which replaces all the other forces acting on an object
How do we calculate resultant force if the forces act in the same direction?
Add them together
How do we calculate resultant force if the forces act in the opposite direction?
Find the difference between them
How do we decide the direction of a resultant force?
The direction of the largest force
What is the resultant force acting on a stationary object?
0 (zero) Newtons
Define speed
How far an object travels in a given time
What are the standard units for speed?
Metres per second (m/s)
Which value is found at the top of the formula triangle for speed?
Distance (metres)
How do we calculate speed using a formula triangle?
Cover speed, we are left with distance and time separated by a division, so speed = distance / time
A car travels 100 metres in 10 seconds. Calculate the car’s speed in metres per second.
Speed = Distance / Time, Speed = 100 / 10 = 10 m/s
How do you convert from metres to kilometres?
Divide by 1000
How do you convert seconds to minutes?
Divide by 60
What is the rule for giving answers as decimals?
Give the same number of decimal places as is given in the question, or as you are told to
Which value is plotted along the y-axis of a D-T graph?
Distance
Which value is plotted along the x-axis of a D-T graph?
Time
What is the difference between an upward and downward sloping straight line?
Upward – object moves away from start Downwards – object moves back to start
What type of line shows us that an object is stationary?
Horizontal, straight line
What does the steepness of a sloping straight line tell us?
The speed
What type of curve shows an object which is accelerating?
A curve which gets steeper
How do we calculate the distance travelled in a D-T graph?
By finding the difference between the start and end of the line along the vertical axis
How do we calculate the time in a D-T graph?
By finding the difference between the start and end of the line along the horizontal axis
How do you determine the total distance from a D-T graph?
The highest point on the graph
How do you determine the total time from a D-T graph?
The furthest point on the graph
State the equation that links speed, distance and time.
Speed = Distance / Time
If distance is measured in km, and time is measured in mins. What are the units for speed?
Km/min
If the units for speed are miles per second. What are the units for distance and time?
Distance is measured in miles, time is measured in seconds
How do speed cameras measure a car’s speed?
Timing how long it takes for a car to travel between two points
Why are speed cameras used on roads and motorways?
To control the speed of traffic
How are instantaneous and average speed different?
Instantaneous speed is the speed at a single point in time, average speed is the speed for the whole journey
Which variable is kept the same in an experiment?
Control
Which variable is measured in an experiment?
Dependent
Which variable is changed in an experiment?
Independent
What is the independent variable in the experiment we are carrying out today?
The height of the ramp
What are the standard units for speed?
m/s
What does a horizontal line mean on a Distance-Time graph?
The object is stationary (not moving)
What is a non-contact force?
A force between two objects which are not touching
Name two forces acting on a toy car as it travels down a ramp.
Gravity/weight, friction, air resistance, reaction force
What is an independent variable?
Variable that is changed in an experiment
Why must control variables be kept the same?
So that they do not affect the results
What is a dependent variable?
Variable that is recorded during an experiment
State two pieces of equipment you can use to measure the dependent variable.
Stop clock and camera phone
How will you decide which piece of equipment to use?
Consider benefits and drawbacks, carry out a practice run to see which gives a more accurate reading
Why do you need to carry out three repeats for each value of the independent variable?
To calculate a mean/average
What is a prediction?
Statement about what you think will happen
Define mass
A measure of the number of particles an object is made of
Define weight
The force of gravity acting on an object
In what direction does the force of weight act?
Downwards
What happens to mass when an object is taken to a different planet?
Nothing, mass stays the same
What happens to weight when an object is taken to a different planet?
Weight changes depending on the GFS of the planet
State the units for gravitational field strength.
Newtons per kilogram, N/kg
What is the gravitational field strength of Earth?
10 N/kg
State the equation that links weight, mass and gravity.
Weight (N) = Mass (kg) x Gravity (N/kg)
What is microgravity?
A situation where the force of gravity is very small
Why do people often think there is zero gravity in space?
Objects appear to float
How do we know that the force of gravity can be felt everywhere?
Planets are kept in orbit around the Sun even though they are millions of miles away
The GFS on Earth is 10 N/kg. What is the Earth’s GFS on the ISS?
90% of this which is 9 N/kg
Why do objects on the ISS appear to float?
They are in free fall towards the Earth
Why doesn’t the space station crash into Earth as it falls?
It travels so fast that it matches the curve of the Earth, so never reaches it
What would happen if the Earth slowed down as it travelled around the Sun?
It would spiral in and crash into the Sun
Give one example of how we can experience microgravity without going into space.
Free fall rides in amusement parks, in a plane travelling up and down very quickly
