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74 Cards in this Set
- Front
- Back
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What is gravitational force also known as? |
Weight |
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What is normal reaction force? |
Force which acts in an upward direction on an object |
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Which unit is force measured in? |
Newton (N) |
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What is the definition of a newton? |
A force of one newton will make a mass of one kilogram accelerate at one metre per second |
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What is air resistance/drag? |
Upward force |
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What is upthrust? |
The upward push of surrounding air |
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What is unbalanced force? |
When two forces cancel each other out as they are the same magnitude and are acting in opposite directions |
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What is a balanced force? |
Forces are the same size but act in opposite directions. |
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What is friction? |
The force which slows moving objects down and finally stops the object. |
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What is a spring? |
Coiled lengths of certain types of metal |
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What will a simple experiment with springs show us? |
Springs change length when a force acts on them and return to their original length when the force is removed. |
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What is Hookes law? |
The extension of the spring is proportional to force? |
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What apparatus did Hooke use? |
He measured the increase in length produced by different load forces on springs. |
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What is elastic limit? |
When a spring starts to stretch more for each successive increase in load force/ |
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What can an unbalanced force also be referred to? |
Resultant force |
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What is force proportional to? |
Force is proportional to acceleration |
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What is acceleration inversely proportional to? |
acceleration is inversely proportional to mass |
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What is the formula combining force, mass and acceleration? |
Force = mass x acceleration |
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How can force, mass and acceleration be rearranged? |
Mass = force x acceleration Acceleration = force / mass |
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What is mass measured in? |
KG |
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What is stopping distance? |
Thinking distance and braking distance |
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What are the factors which affect reaction time? |
1. Driver is tired 2. Driver is under the influence of alcohol or drugs 3. Poor visibility |
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What is the weight of an object? |
The force that acts on it because of gravity
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What is the equation to work out the weight of an object? |
force = mass x acceleration F = m x a and weight = mass x acceleration W = m x g |
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What is 0.1kg in newtons? |
0.1Kg mass is 1N |
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What is weight measured in? |
Newtons (N) |
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What is air resistance or drag? |
The friction force which opposes movement of an object moving through the air |
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What two significant forces do objects falling through the air experience? |
Weight force and drag |
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What is terminal velocity? |
The point where the drag force is exactly balamnced to the weight force. As there is no unbalanced force its falling will not get any faster. |
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What happens when a skydiver opens their parachute? |
The drag force of the parachute is greater than the weight of the skydiver. The unbalanced force acting on the skydiver acts upwards and for a while they will decelerate. As she slows the size of the drag force decreases and eventually a new terminal velocity is reached. |
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How can you investigate terminal velocity? |
You can use a tall measuring cylinder filled with water and drop small glass beads in to it. |
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What is Newtons first law/ |
Things don't speed up, slow down or change direction unless you push or pull them |
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What is Newtons second law?
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The bigger the force acting on an object, the faster the object will speed up. Objects with greater mass require bigger forces than those with smaller mass to make them speed up at the same rate. |
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What is the turning effect?
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Forces are making the object turn around a pivot. |
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What is the turning effect of a forge about a hinge or pivot called? |
Its moment. |
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What is the equation for the moment of a force? |
moment of a force = force x perpendicular distance from pivot Moment = F x d |
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What is the moment of a force measured in? |
Newton metres (NM) |
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What rule has tone followed for an object to be in balance? |
sum of anticlockwise movement = sum of clockwise movements. So if both sides of a seesaw aren't balanced, it will be wonky. |
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What is the centre of gravity? |
The point where an object is balanced, the anticlockwise moment is equal to the clockwise moment but there are no downward forces acting this situation other than the weight of the ruler itself. |
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What kind of orbit do planets follow? |
Elliptical
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What is gravitational field strength? |
The strength of gravity on a planet or moon |
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What is the gravitational field strength of the moon in comparison to earth? |
Earth - 10N/Kg Moon - 1.6N/Kg |
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Why do we see planets? |
Although planets are non-luminous, we see them because they reflect light from the sun. |
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How are planets held in orbit?
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Gravitational pull of the sun |
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How long does it take the moon to orbit earth? |
29.5 days |
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How are moons kept in orbit? |
Gravitational force. |
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What do comets orbit? |
The sun |
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What type of orbit does a comet have? |
Very elongated |
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What do asteroids orbit? |
The sun |
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What do satellites orbit? |
A planet |
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What holds a satellite? |
Gravitational forces |
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How can you calculate the speed of a satellite? |
speed = distance / time |
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How do you work out the distance travelled around an orbit? |
distance = 2 x pi x radius |
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What is the equation for orbital speed? |
orbital speed = (2 x pi x orbital radius) / time orbital speed = (2 x pi x r) / t |
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What is orbital speed measured in? |
km/s |
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What are galaxies? |
Consist of billions of stars |
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What is our galaxy? |
Milky way |
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What is the universe? |
Mainly empty space within which are scattered large numbers of galaxies |
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What are asteroids? |
Minor planets or rocks that orbit the sun |
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What are comets? |
They are dest and ice that orbit the sun |
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*What is a vector quantity? |
A quantity in which its size and direction matter |
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*What is a scalar quantity? |
A quantity in which no direction is associated with them |
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*What are examples of vector quantities? |
displacement velocity acceleration force weight momentum |
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*What are examples of scalar quantities? |
distance speed time power energy Temperature |
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*The resultant force of forces that act along a line |
Resultant force is the overall force acting in a direction on an object. It is best explained by digrams which show that the resulatnt force is the overall force given individual forces acting along a line. |
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What is the formula relating momentum, mass and velocity? |
momentum = mass x velocity p = m x v |
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What is momentum measured in? |
kg m/s |
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How can momentum, mass and velocity be rearranged? |
p = m x v m = p / v v = p / m |
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Momentum and safety features? |
As force = change in momentum / time To decrease the force felt, you would have to increase the amount of time it takes for the force to be felt. In a car, there are various safety features equipped to do this, as they increase the time that the car's momentum takes to reach zero. Some safety features include: seatbelt, airbags and crumple zones |
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Conservation of momentum to calculate the mass, velocity, or momentum of objects |
p = m x v m = p / v v = p / m |
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Relationship relating force, change in momentum and time taken |
force = change in momentum / time taken F = (mv - mu) / t |
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What is Newtons Third Law? |
For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs - equal and opposite action-reaction force pairs. |
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Use the principle of moments for a simple system of parallel forces acting in one plane |
The ‘Principle of Moments’ states that an object will be balanced if the sum of the clockwise moments is equal to the sum of the anticlockwise moments. This means that the moments must balance either side. e.g.Clockwise moments = anticlockwise momentsmoment = force x distance from pivotW x 4 = 0.8 x 24 = 19.2W = 19.2 / 4W = 4.8N |
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Upward forces of a light bean vary with the position of a heavy object placed on the beam |
This means you need to understand that if you have say a plank of wood being held in balance by springs pushing up at the ends and you put a weight on the beam, the springs would have to exert more force as they need to equal the downward force. |
