Chapter 5 - Forces Flashcards
What is a vector and a scaler? (Give also examples of each one)
Vector quantity: is a measurable quantity that has a both magnitude and direction.
Eg~ Speed, Velocity, Distance and Energy.
Scalar: Is a measurable quantity that has only a magnitude, not a direction.
Eg~ Mass, Force and Time.
Study whats on page 75 GOOD NOTES (Use Of Pythagoras)
Also page 76
Study whats on page 75 GOOD NOTES (Use Of Pythagoras)
Also page 76
Experiment for center of mass.
Material:
- Pin
- cardboard
- string
- ruler
- blue tack
First you get a piece of cardboard and cut an irregular shape.
Then we get a piece a pin and you stab it against one of the corners.
After you put a piece of string on the pin that is stabbed against the cardboard and you piece of blue tack so the string doesn’t fall off from the pin.
Then hold the the pin so that the string balances from side to side on the cardboard. When it stops by gravity you draw a line on the mark.
Then you do everything again but at another point.
When both lines crosses each other that is the the center of mass from the irregular shape.
Resultant force
Is the single force that would have the same effect on an object as all the forces that are acting on the object.
Eg: A rock was dropped from the top of a building. The gravitational force pulls down to the ground but the Air Force decreases. Also The Air Force is making it go forwards (At the same time that is going downwards.
1000N (Downwards)
250N (Upwards)
100N (Forwards)
0N (Backwards)
1000N - 250N= 750N
100N - 0N= 100N
This means that whistle the rock is falling rapidly it is going forwards a bit at the same time.
If there was no Air Force going forwards (No wind that day) the rock would hit the floor before.
Work Done equation
When any object is moved around, work will need to be done on it to move (obviously)
Work done triangle is:
W.d=F*D
Equation for Power (NOT FOR AN ELECTRICAL CIRCUIT)
P=W.d ÷ T
What is the spring the constant?
Who’s theory was it?
The experiment is on page 176 in the yellow book.
K= Force÷meter or E= 0.5Ke2
The Hocke’s Law
Triangles for:
Speed (Velocity)
Average speed
S=d÷t
A.S=t.d÷t.t
Speed=Distance÷time
Average speed= total distance ÷ total time
What are the laws of Newton:
1º- Objects in motion tend to stay in motion and objects at rest tend to stay at rest unless acted upon by an unbalanced force.
2º- F=ma / F=(mv)/t
3º- For every action there is an equal and opposite reaction.
Momentum?
Momentum is the product of mass and velocity of an object.
Measured in Kg/m/s.
Symbol for momentum is p
Triangle equation:
P=M*V
Example: A lorry at 10m/s with a mass of 3000kg crashes against a car that is stationed with a mass of 1000kg.
By the impulse of the lorry, the car is travelling at 15m/s with the same mass. (GOOD NOTES page 109)
What velocity did the lorry when the car started moving
P= 3000kg * 10m/s P= 30,000kg/m/s
Then…
V= 30,000kg/m/s ÷ 40,000kg= 0.75 V= 0.75*15m/s V= 11.25m/s
Formula for displacement?
S= (v2 + v2) ÷ 2 * acceleration
S stands for displacement.
Example is:
How far have, travelled on my motorbike if my end speed is 50 m/s and my acceleration is 3m/s2.
S= (0 m/s2 + 50 m/s2) ÷ 2 * 3m/s2
S= (50 + 50) ÷ 6
S= 16 m/s2
What is the equation for acceleration?
Acceleration= (difference) volume ÷ time Acceleration= v ÷ t
What is a sketch graph and velocity-time graph?
It’s a graph with no plotted lines.
And
Shows how the velocity of a moving object changes overtime.
What is uniform motion?
What are the following symbols: S= U= V= A=
Is the constant acceleration
S= displacement U= initial velocity V= final velocity A= acceleration
Equation for weight
W=m*g
