Forces Flashcards
What is happening if the resultant force is 0 on a stationary object
It stays stationary
What is the resultant force
The sum of the forces
What happens to a moving object if the resultant force is 0?
It keeps moving at a constant speed
What happens when the forces aren’t balanced in a stationary object
It begins to move in the direction of the resultant force
What happens to a moving object when the resultant force isn’t 0
It accelerates or slows down depending on the direction of the resultant force
What does acceleration depend on?
Size of the force
The mass
What is acceleration measured in?
M/s2
What is velocity measured in?
M/s
How do you find the distance travelled in a velocity time graph
The area under the graph is the total distance travelled
What is Newton’s first law?
Object stays still unless acted on by unbalanced forces
What is Newton’s third law?
If a body exerts a force on another, there is an equal and opposite force
What is force measured in?
N Newton’s
When there is a horizontal line on a velocity time graph, what does that mean?
Object is moving at a constant speed
When there is a horizontal line on a distance time graph, what does that mean?
Object is stationary
When there is a straight diagonal line going up on a distance time graph, what does that mean?
Object is moving at a steady speed (constant speed)
When there is a straight diagonal line going up on a velocity time graph, what does that mean?
Object is moving at a constant acceleration
When there is a curved line going up on a distance time graph what does that mean?
Object is accelerating
When there is a curved line going down in a distance time graph what does that mean?
Object is decelerating
When there is a curved line going up on a velocity time graph, what does that mean?
Increased rate of acceleration
When there is a curved line on a velocity time graph going down, what does that mean?
Increased rate of deceleration
When there is a diagonal line going down on a velocity time graph what does that mean?
Constant deceleration of object
When there is a diagonal line going down on a distance time graph, what does that mean?
Object is travelling at a steady speed (constant speed) back to the start
The steeper the Line…
The greater the acceleration
How do you calculate the gradient?
Rise/run
What does working out the gradient represent on a velocity time graph
The acceleration
What does the stopping distance of a car depend on ?
Thinking distance and braking distance
What 5 forces act on a car moving at a steady speed?
Weight Reaction force Driving force Friction Air resistance
Which force on a car is pointed down?
Weight (gravity)
Which force on a car is pointing up?
Reaction force
Which forces on a car are indirectly proportional?
Weight(gravity) and reaction force
Driving force and air resistance
Format in drawing resultant force?
E.g.
2N^
3N>
If the driving force is bigger than the air resistance of a car moving, what is the car doing ?
Accelerating
For a car to slow down, what has to happen (2)
The driving force must be reduced
The resistive forces must be increased
How do you work out stopping distance?
Stopping distance= thinking distance+breaking distance
What is thinking distance?
Distance travelling between need for breaking and brakes being pressed
What is breaking distance ?
Distance taken to stop after brakes have been applied
What 3 factors affect thinking distance?
Tired
Distracted
Influence from drugs and alcohol
What 2 factors affect breaking distance?
The cars tyres or brakes are in poor condition
Weather conditions I.e. Icy roads
What happens when the braking distance increases?
Car’s speed increases
What happens when brakes are applied to a car? (3)
Work is done by the friction force
Kinetic energy of the vehicle is reduced because the speed decreases
Increases temperature of the brakes
What is terminal velocity ?
When the resultant force is 0
What are the main 2 forces exerted on falling objects ?
Weight(gravity)
Air resistance
What are the 3 stages of falling (3)
Since in1) object accelerates downwards
No air resistance
2) air resistance increases and becomes bigger than the weight/ force
3) the object’s weight and air resistance is balanced. It reaches a steady speed called terminal velocity
Why does a coin fall faster than a feather ?
The feather is lighter so air resistance increases quickly and it falls at terminal velocity
The coin is heavier so it travels fast before air resistance is large enough to balance the weight. So, it probably hits the ground before terminal velocity
On the moon, what happens when you drop a light object and a heavy object and why?
They land at the same time.
The moons gravity is too weak so there is no air resistance. Therefore, the objects had the same acceleration
On a velocity time graph for falling objects, when a line is horizontal, what does it mean?
Object has reached terminal velocity
What are the 3 stages of dropping something?
1) object accelerates because the force of gravity is bigger than friction force
2) it is still accelerating but acceleration decreases as friction is increasing
3) it stops accelerating and reaches terminal velocity
What is the difference between weight and mass ?
Weight is the result of gravity and is the force acting on mass. measures in N
Mass is how much stuff is in an object measure in kg
What do elastic objects do?
Store elastic potential energy when stretched
What is the relationship between the extension of an elastic object and the force applied?
They are directly proportional
What is the spring constant measured in?
N/m
The greater the spring constant…
The greater the value of K so the stiffer the spring
