Forces Flashcards
(34 cards)
As mass increases, velocity…
Increases
What is the difference between a vector and scalar quantity?
A vector quantity has magnitude AND DIRECTION
A scalar quantity has only magnitude
What is the resultant force?
The result of all the forces acting on the object
True or false: friction does NOT oppose motion
False: friction does oppose motion
What is the relationship between unbalanced force, mass and acceleration?
F = ma
Force = mass x acceleration
What is the relationship between weight, mass and gravitational field strength?
W = mg
Weight = mass x gravitational field strength
Thinking + braking distance
= stopping distance
What affects the thinking distance?
Alcohol/drugs
Speed
Tiredness
What affects braking distance
Road condition (wet or icy)
Car condition (brakes)
Mass of car
Speed
Describe the forces acting on falling objects (and explain why falling objects reach a terminal velocity)
- At the start there is only weight acting downwards.
- Therefore there is a large resultant force downwards. Since F = ma there is a large acceleration for the same mass.
- As the skydiver speeds up (/accelerates), air resistance (upwards) increases.
- Eventually the downward weight balances the upward air resistance
- Therefore the resultant force is zero. Since F = ma acceleration is zero for the same mass and they travel at a constant speed or terminal velocity.
Hooke’s law (spring/elastic band and weight experiment)
When force increases, extension…
Increases
Linear is…
Straight line
Non-linear is…
Curved line
The straight line through the origin on force extension graphs…
Obey Hooke’s law
The non-linear part of force extension graphs…
Does not obey Hooke’s law
Where the line stops on force extension graphs is the…
Elastic limit - the elastic/spring/wire breaks
State Hooke’s law.
Force is proportional to extension
Explain how extension of the spring is calculated in the Hooke’s law experiment.
Extension = length - original length
(Ext = l - lo)
On cars/cyclists, instead of:
Weight - downwards
OR
Upthrust - upwards
It is…
Traction - left or right
Where the line is just straight, and does not go any higher on velocity time graphs, it is..
The terminal velocity
If a block’s initial velocity (u) is 10 m/s to the left, and then 500N of force to the right is applied to it, what would happen?
It would decelerate
If a 18kg block’s initial velocity (u) is 10 m/s to the left, and then 500N of force to the right is applied to it, calculate the acceleration of the block.
F = ma
A = F/m
500N/18kg = -27.8 m/s^2
(It’s negative because it’s going to the left and decelerating )
State the equation that links acceleration, final velocity, initial velocity and time.
A = (v-u)/t
If a block’s initial velocity (u) is 10 m/s to the left, and then 500N of force to the right is applied to it, calculate the final velocity of the block after 30 seconds.
(The block’s acceleration is 27.8m/s^2)
A = (v-u)/t
V = at+u
(27.8 x 30)-10m/s
= 824m/s
(Ps I’m not sure about this I thought it was -844 but idk)
