Forces And Motion Flashcards
(28 cards)
What does a straight line on a distance time graph indicate?
Constant speed
On a D-T graph what does a curve indicate?
Change in speed
How do you calculate the speed on a D-T graph?
Speed = Gradient = difference in y/ distance in x
Equation for average speed?
Average speed = total distance/total time
Equation for acceleration.
Acceleration = change in velocity / time taken
Or
Acceleration = (final velocity - initial velocity) / time taken
What is the unit for acceleration?
Units: m/s^2
How do you calculate acceleration on a V-T graph?
Acceleration = gradient = difference in y/difference in x
Which direction does the line go on a V-T graph when accelerating?
Positive
Which direction does the line go on a V-T graph when deccelerating?
Negative
How do you calculate the distance on a V-T graph?
The area under the line represents distance
Equation for calculating uniform acceleration?
To calculate v: v^2 = u^2 + 2as
To calculate a: a = (v^2 - u^2) / 2s
V= final velocity
U= initial velocity
S= distance moved
When is the uniform acceleration equation needed?
When the time taken is not known
Definition of a scalar?
Quantities that have magnitude but not direction
What is a vector?
Quantities that have both magnitude and direction
What is the difference between speed and velocity?
Speed is a measure of te distance traved per unit time, regardless of the direction, scalar
Velocity is a measure of the displacement of and object per unit time, including the direction, vector
How do you calculate resultant force?
Forces moving opposite directions, you subtract
Forces moving the some direction , you add
What three things may happen when there is a resultant force on an object?
The object might speed up
The object might slow down
The object might change direction
What equation links resultant force mass and acceleration?
F=ma = delta P (momentum)/ delta t(time taken)
= m(v-u)/delta t
What is the equation linking weight, mass nad gravatational field strength?
W = mg
What is Terminal velocity?
The fastest speed an object can reach when falling.
Reached when the upwards and downwards forces are balanced; resultant force equals 0, meaning it can no longer accelerate and a constant terminal velocity is reached.
Why does the air resistance increase when speed increases when falling?
Because the object collides with the air particles as it moves through the air; the faster the object the more collisions in ha with the air particles.
A sky diver is falling through the air. Explain what is happening in terms of foces and terminal velocity?
- As soon as the diver steps out of the plane they begin to fall at the maximum acceleration as only weight is acting on them.
- As the sky diver begins to fall, the air resistance is very small because the sky divers speed is small.
- As the sky diver accelerates, their speed increases, so the force of air resistance increases
- The sky diver’s acceleration decreases, their speed increases at a slower and slower rate.
- Eventually the sky diver reaches a speed whee the air resistance and thir weight is balanced, so the resutant force is zero.
- This is terminal velocity.
Describe a method used to investigate force and extention for springs and rubber bands.
- Align the marker to a value on the ruler with no mass added, and record this initial length of the spring / rubber band
- Add the 100 g mass hanger onto the spring / rubber band
- Record the mass (in kg) and position (in cm) from the ruler now that the spring / rubber band has extended
- Add another 100 g to the mass hanger
- Record the new mass and position from the ruler now that the spring / rubber band has extended further
- Repeat this process until all masses have been added
- Remove the masses and repeat the entire process again, until it has been carried out a total of three times, and an average length (for each mass attached) is calculated
State Hooke’s Law:
The extention of an elastic object is directly propotional to the force applied, up to the limit of proportionality.
