Combined Physics - P5 Forces Flashcards
What two things does a force arrow show?
- The length of the arrow shows the size of the force.
- The direction of the arrow shows the direction of the force.
Give some examples of non-contact forces
- Gravitational force
- Electrostatic force
- Magnetic force
What is a ‘resultant force’?
The sum of all forces acting on an object
(the overall force acting on an object)
What equation links force, spring constant and extension?
Force = spring constant x extension
F = k e
Give some examples of contact forces
- Friction
- Air resistance
- Tension
- Normal contact force
What are the units for:
a) gravitational field strength
b) weight
c) mass
a) N/kg
b) N
c) kg
What is the equation that links work done, force and distance?
Work done = force x distance
W = F s
What equation links weight, mass and gravitational field strength?
Weight = mass x gravitational field strength
W = m g
Why type of energy is stored in a spring that is stretched or compressed?
Elastic potential energy
What happens to the temperature of an object experiencing friction?
Temperature increases
What is the name of an object that:
a) will return to its original shape after being deformed
b) will not return to its original shape after being deformed
a) elastic
b) inelastic
What is the relationship between force and extension of an elastic object?
Directly proportional
What happens to air resistance as speed increases?
As speed increases, air resistance increases.
What are typical speed values for someone walking, running and cycling (m/s)?
- Walking 1.5 m/s
- Running 3 m/s
- Cycling 6 m/s
What is the speed of sound?
340 m/s
How many forces need to to be applied to this spring to stretch or compress it?
Two forces (e.g. one at either end)
What equation links acceleration, final velocity, initial velocity and time?
What equation links distance travelled, speed and time?
Distance travelled = speed x time
s = v t
Why does a falling object reach terminal velocity?
- The resultant force on the object is zero.
- Forces of weight and air resistance are balanced.
Name the point on the graph labelled ‘X’
Limit of proportionality
Describe the motion in the following distance-time graph at points a, b, c and d.
a) constant speed
b) stationary
c) accelerating
d) decelerating
If you wanted to investigate how mass affects acceleration, what part of the equipment would you change?
The mass of the trolley (by adding more masses to the trolley).
Which part of the equipment measures acceleration?
Light gate
If you wanted to investigate how force affects acceleration, what part of the equipment would you change?
The force pulling the trolley (by adding more masses to the hook).
What is the equation for Newton’s Second Law that links force, mass and acceleration?
Force = mass x acceleration
F = m a
Give three factors that can affect braking distance.
- Road conditions
- Weather conditions: wet / icy roads
- Vehicle conditions: condition of brakes / tyre tread depth
What equation links momentum, mass and velocity?
Momentum = mass x velocity
p = m v
What happens if a car undergoes a large deceleration?
Brakes overheating / loss of control
Describe the motion of a moving car experiencing balanced forces.
Keep moving at a constant speed
Describe the motion of a moving car experiencing unbalanced forces.
The car will change speed (either accelerate or decelerate)
Describe the motion of a stationary car experiencing balanced forces.
The car will remain stationary.
Describe the motion of a stationary car experiencing unbalanced forces.
The car will accelerate.
What are typical everyday speeds for cars, trains and planes?
- Car 25 m/s
- Train 55 m/s
- Plane 250 m/s
What is stopping distance?
The sum of the thinking distance and the braking distance
What is braking distance?
The distance covered during the braking force.
What are ‘typical’ reaction times?
0.2 s to 0.9 s
What is Newton’s Third Law?
Whenever two objects interact, the forces they exert on each other are equal in size and opposite in direction.
What is thinking distance?
The distance covered during the driver’s reaction time.
How does speed affect stopping distance?
Stopping distance increases with speed.
Give three factors that can affect a driver’s reaction time.
- Tiredness
- Drugs
- Alcohol
What is work done the same as?
Energy transferred
If your mass on Earth is 50 kg, what would be your mass on the moon?
The same, 50 kg.
Your mass does not change.
What are the units for:
a) force
b) acceleration
c) weight
d) mass
a) N
b) m/s2
c) N (weight is a force)
d) kg
Name the forces acting on the book.
Calculate the resultant force on the box
0 N (there is no resultant force)
Calculate the resultant force on the box.
2N to the left
Describe the experiment to investigate how force affects the extension of the spring.
- Measure the starting length of the spring using the ruler.
- Add one 10 g mass, measure the extension of the spring using the ruler.
- Repeat 5 times, each time adding one 10 g mass and measuring the extension of the spring.
Higher Q. What is inertia?
The tendency of objects to continue in their state of rest / uniform motion
Higher Q. How can the displacement of an object (the distance travelled) be calculated from a velocity-time graph?
The area under a velocity-time graph
Higher Q. What is inertial mass?
A measure of how difficult it is to change the velocity of an object.
Higher Q. How can the motion of an object in a circle be described?
Constant speed but changing velocity
