Force and Motion

Created by

ben

Cards (29)

Does a distance quantity require a specific direction? i.e. is it a scalar or vector quantity?
No specific direction is required so it is a scalar quantity.
If an object moves 3 meters to the left and then 3 meters back to its inital position, what is the objects displacement?
Zero
Displacement is a vector quantity so involves direction
Object starts and ends in the same point
State the value of the speed of sound?
330 m/s
What is typical human walking speed?
1.5 m/s
What is a typical value for human running speed?
3 m/s
Typical value of human cycling speed?
6 m/s
Equation that links speed distance and time?  
Distance (m) = Speed (m/s) × Time (s)
Why can an object travelling at a constant speed in a circle not have a constant velocity?
Speed is a scalar quantity
Velocity is a vector quantity which means it can only be constant f the direction is constant
In circular motion, the direction is continuously changing.
How can speed be calculated from a distance-time graph?
The speed is equal to the gradient of the graph.
What must be done to calculate speed at a given time from a distance-time graph for an accelerating object?
Draw a tangent to the curve at the required time
Calculating gradient of the tangent
State the equation for the average acceleration of an object.
Acceleration (m/s²) = Change in velocity (m/s) / Time (s)
How can the distance travelled by an object be calculated from a velocity-time graph?  
It is equal to the area under the graph.
Give an approximate value for the acceleration of an object in free fall under gravity near the Earth's surface.
9.8 m/s²
What can be said about the resultant force acting on an object when it is falling at terminal velocity?
Resultant force is zero.
The object is moving at a constant speed and so isn't accelerating
State newton's first law for a stationary object.
If the resultant force acting on an object is zero, the object will remain at rest.
State Newton's first law for a moving object.
If the resultant force on a moving object is zero, the object will remain at a constant velocity (same speed in same direction).
If an object changes direction but remains at a constant speed, is there a resultant force?
Since there is a change in direction, there is a change in velocity and so there must be a resultant force.
What is inertia?
The tendency of an object to continue in its state of rest or uniform motion.
Define the equation for Newtons second law.
Resultant Force = Mass × Acceleration
F = ma
What is inertial mass?
A measure of how difficult it is to change a given object's velocity
The ratio of force over acceleration
State Newton's third law.
Whenever two objects interact, the forces that they exert on each other are always equal but opposite.
What is the stopping distance of a vehicle equal to?
Braking + Stopping distance
For a given braking distance, if the vehicle's speed is increased, what can be said about its stopping distance?
The stopping distance is increased with an increase in speed.
Give a typical range of values for human reaction time.
0.2 seconds - 0.9 seconds
Give three factors which can affect a driver's reaction time..
Tiredness
Drugs
Alcohol
Give two factors that may increase braking distance.
Adverse (wet/icy) road conditions
Poor brake/tyre conditions
Describe the energy transfers that take place when a car applies its brakes.
Work is done by the friction force between the brakes and wheel.
Kinetic energy of the wheel is converted into heat and dissipated to the surroundings through brake discs.
To stop a car in a given distance, if its velocity is increased, what must happen to the braking force applied?
The braking force must also be increased.
State two consequences of a vehicle undergoing very large decelerations.
Kinetic energy is converted into heat ia every high and causes brakes to overheat
Loss of control of the vehicle