76 terms

Each out of scalars or vectors have direction?

Vectors

Give an example of a scalar quantity

Mass, temperature, time, length/distance, speed, energy

Give an example of a Vector quantity

Displacement, velocity, force, acceleration, momentum

When you add two or more vectors together what do you find?

The resultant vector

In what ways can you find the resultant vector?

Scale drawings or Pythagoras and trigonometry

Explain how to set up a scale drawing to find the resultant vector

Draw each vector, to scale, tip-to-tail. Then draw the resultant vector from the tail of the first of the tip of the last and measure its length and angle.

Explain how you can find the resultant vector using Pythagoras/trigonometry

When two vectors are at right angles to each other, you can us Pythagoras/trigonometry to find the resultant vector

If a body is in equilibrium what will the forces acting on it be?

The forces must be in equilibrium

What does resolving a force mean?

Splitting the force into component form

How can you draw three coplanar forces acting on a body in equilibrium?

You can draw the forces as a triangle, forming a closed loop

If two forces are acting on an object, how do you find the resultant force?

By adding all the vectors together and creating a closed triangle (with the resultant force represented by the third side)

What does the moment of a force depend on?

1) Size of force

2) how far the force is applied from the turning point

2) how far the force is applied from the turning point

What does the principle of moments state?

The principle of moments state that for a body to be in equilibrium, the sum of the clockwise moments about any point equals the sum of the anti-clockwise moments about the same point

Describe the forces acting on a lever

In a lever, an effort force acts against a load force by means of a rigid object rotating around a pivot

What does coplanar mean?

All in the same plane

What is a couple?

A couple is a pair of coplanar forces of equal size which acts parallel to each other, but in opposite directions

What does a couple produce?

A turning effect

Define mass

The mass of an object is the amount of 'stuff' in it

The greater the objects mass, is it's resistance to a change in velocity greater or lesser?

Greater

Define inertia

The resistance to a change in velocity

Does the mass of an object change if the strength of the gravitational field changes

No

Weight is the forced experienced by...

A mass due to gravitational field

Does the weight of an object change if the strength of the gravitational field changes

Yes

Define centre of mass

The centre of mass of an object is the point where you can consider its whole weight to act through

Where is the centre of mass in a uniform, regular solid

At its centre

How do you find the centre of mass in a regular object?

1) use symmetry

2) the centre of mass is at the centre where the lines of symmetry will cross

3) the centre of mass is halfway through the thickness of the object where the lines meet

2) the centre of mass is at the centre where the lines of symmetry will cross

3) the centre of mass is halfway through the thickness of the object where the lines meet

How do you find the centre of mass in an irregular object?

1) hang the object freely from a point

2) using a plumb bop draw a vertical line downwards from the point of suspension

3) hang the object from a different point and repeat

4) the COM is where the lines cross

2) using a plumb bop draw a vertical line downwards from the point of suspension

3) hang the object from a different point and repeat

4) the COM is where the lines cross

When will an object topple over?

If the vertical line drawn downwards from its centre of mass falls outside its base area. As a resultant moment occurs, which provides a turning effect

What conditions causes an object to be stable?

Low centre of mass

Wide base area

Wide base area

Define speed

How fast something is moving regardless of direction

Define displacement

How far an object has travelled from its starting point in given direction

Define velocity

The rate of change of an objects displacement (speed in a given direction)

Define acceleration

The rate of change of an objects velocity

How is acceleration displayed on a displacement-time graph

A curved line

How is velocity displayed in a displacement time graph

The gradient

How do you find the instantaneous velocity on a displacement time graph which displays the acceleration of a car

You need to draw a tangent to the curve at that point to find its gradient

How is acceleration displayed on a velocity time graph

A straight line

How is changing acceleration displayed on a velocity time graph

A curved line

How is displacement displayed on a velocity time graph

Area under the graph

What does the area under the an acceleration time graph show

The change in velocity

What piece of experiment can you use for motion experiments

An ultrasound position detector, a type of data logger that automatically records the distance of an object from the sensor several times a second

Give three advantages of using data loggers over traditional methods

1) more accurate- don't need to wait for human reaction times

2) automatic systems have a much higher sampling rate than humans

3) you can see the data displayed in real time

2) automatic systems have a much higher sampling rate than humans

3) you can see the data displayed in real time

What is the only force acting on an object in free fall

Weight

What did Galileo set up to test his theory?

Galileo set up systematic and rigorous experiments. These experiment could be repeated and the results described mathematically and compared

Galileo believed that all objects fall at the same rate. But struggled to prove this as objects fall to quickly. How did he over come this problem?

He measured the time a ball took to roll down a smooth groove in an inclined pane. This slowed the balls fall as well as reducing the effect of air resistance

How do you find 'g' from a displacement time graph?

Finding the change in the gradient between two points on the graph

What's the method for working out projectile motion problems which start off at angle?

1) resolve the initial velocity into horizontal and vertical components

2) use the vertical components to work out how long it's in the air and/or how high it goes

3) use the horizontal component to work out how far it goes horizontally while it's in the air

2) use the vertical components to work out how long it's in the air and/or how high it goes

3) use the horizontal component to work out how far it goes horizontally while it's in the air

What's Newton's 1st law state?

That the velocity of an object will remain constant unless a resultant force acts on it

What does Newton's second law state?

Acceleration is proportional to the force (That the more force you have acting on a certain mass the more acceleration you get and for a given force the more mass you have the less acceleration you get)

Is acceleration Independent or dependent of he mass?

Independent

What does Newton's third law state?

If an object A exerts a force on object B, then object B exerts an equal but opposite force on object A

For Newton's 3rd law what do the two forces have to be?

The forces have to be of the same type

What are the two mains types of friction

Fluid and dry friction

What does fluid/dry friction depend on?

1) thickness/viscosity of the fluid

2) it increases as speed increases

3) depends on the shape moving through it- larger area=larger resistance

4) A projectile is slowed down by air resistance

2) it increases as speed increases

3) depends on the shape moving through it- larger area=larger resistance

4) A projectile is slowed down by air resistance

What should you remember about frictional forces

1) it always opposes motion

2) never speeds things up/start it moving

3) convert kinetic energy into heat and sound

2) never speeds things up/start it moving

3) convert kinetic energy into heat and sound

What is the lift force

Lift is an upwards force on an object moving through a fluid

When does lift happen

Happens when the shape of an object causes the fluid flowing over it to change direction

In what direction does the lift force act compared to the direction the fluid flows in

Perpendicular

How does a car reach terminal speed

1) car accelerates from rest using a constant driving force

2) As speed increases, friction increases - reducing the restaurant force acting on the car and reducing its acceleration

3) frictional forces become equal to the driving force - now no resultant force and no acceleration so the car has a constant speed

2) As speed increases, friction increases - reducing the restaurant force acting on the car and reducing its acceleration

3) frictional forces become equal to the driving force - now no resultant force and no acceleration so the car has a constant speed

What are two ways to increase a car maximum speed

1) increasing the driving force

2) reducing the frictional force

2) reducing the frictional force

What does the momentum of an object depend on?

mass and velocity

the total momentum of two objects before the collision equals..

The total momentum after the collision.

What is conserved in an elastic collision

Momentum and kinetic

What is conserved in an inelastic collision

Momentum only

Newton's 2nd law of motion states that force is the rate of change in momentum...

Of an object is directly proportional to the resultant force which acts on the object

What does impulse equal

Change in momentum

How is impulse displayed on a force-time graph

The are underneath

How can the force of an impact be reduced

By increasing the time of impact

How do crumple zones work

The parts at the front and back of the car crumple up on impact. This causes the car to take longer to stop, therefore increasing the impact time and decreasing force of passengers

How do seat belts work

They stretch slightly increasing the time taken for the wearer to stop. Reduces forces acting on the chest

How do air bags work

These slow down passengers more gradually, and prevent them hitting hard surfaces inside the car

What does work mean

Means the amount of energy transferred from one form to another when a force causes a movement of some sort

How is work done displayed on a force displacement graph

Area underneath

Define power

The amount of energy transferred from one form to another per second

Define watt

Rate of energy transfer equal to 1 joule per second

What does the principle of conservation state

Energy cannot be created or destroyed. Energy can be transferred from one form to another but the total amount of energy in a closed system will not change