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80 Cards in this Set
- Front
- Back
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Where does weight act (to and from)? |
towards the centre of gravity (e.g.. towards the earth)And form a centre of mass |
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What 2 things does every force have? |
Magnitude and direction (e.g. velocity) |
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What is a vector |
A force (And something that has both magnitude and direction) |
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What is a scalar |
Something that only has magnitude (e.g.. speed) |
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How are forces usually represented in diagrams? |
As arrows (longer for larger forces) |
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What is weight? |
The force acting on a mass |
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Is mass scalar or vector? |
Scalar |
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What is displacement? |
The distance an object has moved from where it started (in a straight line) |
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What does speed tell you? |
Distance covered in a certain time |
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What does velocity tell you? |
Speed in a direction (e.g.. 50 mph South East) |
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When an object goes round a bend at a constant speed, why is its velocity changing? |
Because the direction is changing |
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What is acceleration (equation and definition)? |
Acceleration= mass × velocity |
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What is acceleration? |
A measure of how fast velocity is changing? |
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What is momentum? |
A combination of mass and velocity and how difficult it is to stop |
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How is average speed calculated? |
S = d/t |
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What is instantaneos speed? |
The speed at a specific point in a jouney |
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How would you measure the speed of a very fast moving object? |
Using light gates |
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What graph can a jorney be shown |
a distance time graph |
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What does a strait line mean? |
The object is not moving |
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What does a strait diagonal line mean? |
Moving at a constant speed |
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What is the gradient reperesenting on a distance time graph |
Speed the object is moving |
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How is gradient calculated |
Change in y/ change in x |
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What does acceleration tell you |
Change in velocity each second |
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What is acceleration measured in? |
m/s^(2) |
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What equatio for acceleration |
Change in velocity(m/s)/ time taken(s) a = (v-u)/t a = acceleration v = final velocity u = initial velocity t = time for change in |
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A runner starts to sprint while jogging and his velocity changes from 2m/s to 6m/s in 4 seconds |
1m/s^(2) |
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What is a resultant force? |
The total force that results from two or more forces acting upon a single object. Found by adding forces, taking into account directions, another term for net force |
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How do you work out a resultant force that has one arrow going up or down and the other going right or left? |
Using Pythagoras' Theorem |
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What is it called if the resultant force = 0 |
Equilibrium (balanced forces) |
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What is it called if the resultant force != 0? |
The forces are unbalanced |
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What do the following mean on a velocity tome graph? a)horizontal line b)diagonal line going up (same gradient) c) diagonal line going down (same gradient) |
a)constant velocity b)constant positive acceleration c)constant negative acceleration (deceleration) |
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Fill in the blank: The steeper the line the greater the _________? |
Acceleration |
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What under a velocity time graph = distance object has travelled? |
Area |
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Equation for final velocity(v) with initial velocity(u), acceleration(a), distance(x) |
v^(2) = (2*a*x) + u^(2) or V^(2)- u^(2) = 2*(a * x) |
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car going at 15m/s accelerates 1.5m/s^(2) over a disstance of 50m/s, what is the velocity? |
v^(2) = (2*1.5*50) + 15^(2) = (150) + 225 = 375 v = square root of 375 = 19.365 (3d.p.) |
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what is the equation for distance that is adapted from the previous question? |
v^(2) - u^(2)/2 * a = x |
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What is Newtons 1st Law? |
A moving object will continue to move at the same speed and direction unless an external force act upon it |
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What is the motion of a body when the resultant force = 0 |
Will move at a constant velocity of will be at rest |
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What is the motion of a body when the resultant force != 0 |
The speed and/ direction will change |
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What is Newtons 2nd Law |
f = m*a |
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What is force measured in? |
kgm/s^(2) or N |
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Equation for weight |
Weight(N) = Mass (kg) * Gravitational Field Strength (N/kg) |
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When an object falls, at what point will it stop accelerating? |
When it has reached terminal velocity |
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What is terminal velocity |
When air resistance and buoyancy = downward force of gravity when travelling through a fluid (commonly air, which has 0 acceleration) |
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How can reaction times be measured? |
Produce a stimulus (sound or light) and someone has to push a button or brake and this time can be measured |
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Equation for inertial mass? |
Inertial mass = Force/ acceleration (force needs to be changes to m/s) |
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A force 160N on a bike produces 2m/s of acceleration. What is the inertial mass? |
IM = F/a = 160/2 = 80Nm/s^(2) |
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What is the equation to calculate force? |
F = ma |
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What is 1N? |
1kg/ms^(2) |
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How much force is needed to give an object weighing 200kg an acceleration of 7m/s |
F = ma = 200 x 7 = 1400N |
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Finish the sentence: For the same mass, the bigger the force __________________________. |
The bigger the acceleration |
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Finish the sentence For the same force, the more massive an object __________________________. |
The smaller the acceleration |
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Method for a practical to investigate acceleration (and this shows that the mass of a trolley effects the acceleration) |
1. Raise one end of the ramp and place a trolley on it. when the ramp is at a height where the trolley just starts to move on it's own, leave it at that height. 2. Set up light gates and a pulley system 3. Stick a piece of card to the trolley, measure the cards length and record it 4. Record mass of trolley 5. Release trolley and write down speed of trolley (from light gates) 6. Put mass on trolley (from the end of the string ) 7. Do 5 for other masses 8. This shows how mass effect acceleration 9. move masses from the string to the trolley and repeat |
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What do you need to do with the overall mass? |
You keep it the same |
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How do you keep the mass the same? |
You move mass from the string (which is where you are storing it) onto the trolley |
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When 2 objects interact, what type of forces are there? |
Action reaction pairs (forces) |
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What are action reaction forces? |
Pairs of forces on interacting objects. Action reaction forces are always the same size, in opposite directions and acting on different objects. They are not the same as balanced forces (which act on a single object) |
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What is equilibrium? |
What a situation is not changing because all of the things affecting it balance out |
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What is the difference between action reaction forces and balanced forces? |
Action reaction forces act on different objects but balanced forces act of one object |
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What is momentum? |
The mass of an object multiplied by \its velocity and is a vector measured in kg m/s |
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Equation for momentum? |
Momentum = velocity x mass p = vm |
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What happens to the momentum in collisions where one object was stationary and another object colides and the stick and move together? |
It stays the same |
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What is the defenition for the conservation of momentum? |
The total momentum of moving objects before a collision is the same as the total momentum afterwards as long as no external forces are acting |
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What are explosions? |
Where 2 colliding objects move away |
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A gun fires a bullet that weighs 0.05kg and is fired at a velocity of 300m/s and the gun weighs 0.5kg. What is the recoil of the gun? |
momentum (of each object) p = mv = 0.05 x 300 = 15kg m/s v(of gun) = p/m = 15/0.5 = 30m/s backwards |
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When 2 objects push against each other and travel in the opposite direction, what is the momentum and why? |
0 because they cancel each other out |
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What is an equation for force using acceleration? |
Force = (Mass x change in velocity) / time or Force = (m(v-u)) / t |
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Because m x v = momentum how else could you write the equation? |
F = chane in momentum / time or F = (mv-mu) / t |
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When object a has a momentum of X and collides with object b, when the two stick and travel together, what is the momentum of objects a and b together assuming there are no external forces? |
X |
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What is thinking distance? |
The distance travelled by the vehicle while the driver reacts |
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What is breaking distance? |
The distance travelled by a vehicle while the breaks are working to bring it to a halt |
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What is the stopping distance? |
The distance in which a vehicle stops , which is the sum of the thinking and breaking distance |
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What factors effect stopping distance? |
Mass of vehicle (and passengers) Speed of vehicle Drivers reaction time State of vehicles breaks State of road State of tyre Amount of friction between tyre and road |
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What are things that would effect thinking distance? |
Drugs, alcohol, tiredness, distractions |
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Why is there a larger stopping distance / breaking distance for higher speeds? |
Because it takes longer to slow to a halt because there is more energy for the breaks to dissipate to the surroundings which will take longer and therefore allow the vehicle to travel further |
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what sort of distances are there folr 30mp/h and 60 mp/h a)Thinking b)Breaking c)Stopping |
a) 30: 9m 60: 18m b) 30: 14m 60: 55m c) 30: 23m 60: 73m |
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What factor does breaking distance go up by when you double speed? Why? |
x4 When you double something and the square it, that number sould be 4x larger than the 1st number squared (eg. 2^(2) = 4^(2) / 4) This happens for this becuase KE = (1/2)mv^(2) |
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What are dangers for large, quick deceleration? |
Whiplash |
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Equation for work? |
W(J) = F(N) x d(m) |
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What is work done = to to bring a vehicle to rest? |
Initial Kinetic Energy |
