Motion and Forces Flashcards
What is a scalar quantity?
A quantity that has a magnitude (size) but no direction.
What is a vector quantity?
A quantity that has a magnitude (size) and a direction
Give some examples of vector quantities.
Force
Velocity
Displacement
Weight
Acceleration
Momentum
Give some examples of scalar quantities.
Speed
Distance
Mass
Energy
Temperature
Time
What is the difference between speed and velocity?
Speed is how fast you are going and has no direction whereas velocity is speed in a given direction
1) Speed =
2) Distance =
3) Time =
1) Speed = Distance / Time
2) Distance = Speed x Time
3) Time = Distance / Speed
How to calculate acceleration?
a = (v - u) / t
a = Acceleration
v = Final Velocity
u = Initial Velocity
t = Time
How to calculate constant acceleration?
v^2 - u^2 = 2 x a x X
X = Distance
Velocity-Time graph
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How to calculate distance travelled from a distance-time graph?
Split the area under the graph into shapes and find the area for each shape and add them together.
How can light gates measure speed and acceleration?
Speed:
The light gate sends a beam of light from one side of the gate to a detector on the other side. When something passes through the gate, the beam of light is interrupted. The light gates measure how long the beam was undetected.
To find the speed, connect the light gate to a computer.
How can light gates measure speed and acceleration?
Acceleration:
Use an object that interrupts the signal twice in a short period of time. The light gates measures the speed for each section and calculates acceleration.
What is Newton’s First Law?
If the resultant force on a stationary object is zero, the object will remain stationary.
If the resultant force on a moving object is zero, it’ll just carry on moving at the same velocity.
What is Newton’s Second Law?
Larger the resultant force acting on the object, the more the object accelerates. Force and acceleration are directly proportional.
Acceleration is also inversely proportional to the mass of the object - Larger mass will accelerate less.
**Formula:*
F = m x a
F = Resultant force
m = Mass
a = Acceleration
What is Weight?
The force acting on an object due to gravity.
Weight is a force measured in newtons.
What is the formula for Weight?
Weight = mass x gravitational field strength
Gravitational field strength on earth is 10 N/kg
How is weight measured?
Weight can be measured using a calibrated spring balance or a newton meter.
Practical : Investigating the relationship between force, mass and acceleration by varying the masses added to trolleys
- Measure mass of the trolley and the hanging hook. Measure the length of the piece of card which will interrupt the light gates
- Adjust the height of the ramp until the trolley starts to move down by itself
- Mark a line on the ramp just before the first light gate
- Attach the trolley to the hanging mass using a string. Hold the trolley still at the start line and let go
- Each light gate will record the time when the trolley passes through. The acceleration can be found out using acceleration = change in speed / time
If a object is travelling at a constant speed, is the velocity changing?
No, if an object is travelling in a circle at a constant speed, it is constantly changing direction, so it is constantly changing velocity. This mean it’s constantly accelerating and there must be a resultant force acting on it.
What is Centripetal force?
Force that keeps something moving in a circle.
What is inertial mass?
Measures how difficult it is to change the velocity of an object. Inertial mass can be found using Newton’s second law rearranging to give m = f / a, this means it is just the ration of force over acceleration.
