Topic 5 - Forces part 2 Flashcards
(34 cards)
What are the typical values for the speed of walking, running and cycling and sound of air?
Walking - 1.5m/s
Running - 3m/s
Cycling - 6m/s
Sound of air - 330m/s
What is a non- uniform motion?
The motion in which the speed is not constant
How do you calculate average speed for non- uniform motion?
Average speed = total distance / total time
What is the difference between speed and velocity?
Speed is a scalar quantity (magnitude), velocity is a vector quantity (magnitude and direction)
What is the difference between distance and displacement?
Distance is the length of the total journey (scalar)
Displacment is the straight line distance between the start and ed points of the journey (vector)
How do you calculate average velocity?
Average velocity = displacment / time
v = s/t
What is acceleration?
The rate at which an objects velocity changes (m/s)
How do you calculate acceleration?
Acceleration = change in velocity / time
How can something be moving at a constant speed but changing velocity at the same time?
An object moving in a circular motion (e.g sun) at a steady speed. It dosent have the same constant velocity becuase velocity is a vector quantity and the direction of the journey is constantly changing, if the velocity change son the object it is accelerating.
What does a distance time graph tell us?
Straight line - object is at a constant speed the gradient tells us the speed, the steeper the line the faster the object is moving
Horizontal line - object is stationary, a line with a increasing gradinet means the object is accelerating and when decreasing its decelerating
How do you determine the speed of an object undergoing uniform motion over a period of time?
The gradient
How do you determine the speed of an object undergoing non-uniform motion at a particular point in time?
Draw a tangent to the curve at the time you are interested in then determine the gradient of the tangent
What is the equation for gradient?
Gradient = rise / run
What does a velocity time graph tell us?
Straight sloping line - object is moving at a constant acceleration, the steeper the line the larger objects acceleration
Horizontal line - objects is moving at a constant speed.
What if the acceleration is constant?
If the acceleration is constant then v(squared) - u(squared) = 2as (s=displacement)
How do you determine distance travelled from a speed time graph?
Can be obtained by determining the area under a speed-time graph, if the line is not straight then it can be determined by counting squares
What is Newton’s first law?
Newtons first law tells us A
an object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force
What is Newton’s seccond law?
The acceleration of an object is directly proportinal to the resultant force acting on it and inversely proportional to the mass
What is intertial mass?
A measure of how difficult it is to change an objects velocity
resultant force / acceleration that force generates
How can Newtons second law be vertified experimentally?
The car:
- The ramp needs to be compensating for friction by tilting so the car travels at a steady speed
- Measure the acceleration: light gate, pulley wheel, weights, string
1. let the car go and as soon as it goes past the light gate stop it and catch the weights, once throught the gate it will record the times and repeat.
What happens to the forces and acceleration of a falling object?
It will freefall due to gravity, and will accelerate at 9.8m/s
If the speed continues to increase, it will eventually the reulatnt force on the object is ZERO as it stops accelerating, then it is traveling at terminal velocity
What is stopping distance?
The total distance required to stop a moving vehicle
Stopping distance = thinking distance + braking distance
What factors affect thinking distance?
- Speed (faster you go the further you travel)
- Drugs/Alcohol ( reaction time)
- Tiredness/illness ( reaction time)
- Distractions (mobile phones)
What factors affect braking distance?
- Speed (faster you go the further you travel)
- Condition (breaks, tyres)
