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Flashcards in Movement Y10 Deck (29)
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What is speed?

Distance ÷ time


What is the difference between speed and velocity?

Velocity has a direction, speed does not


What is acceleration?

How fast an object changes its velocity
Acceleration = (velocity final - velocity initial) ÷ time
Measured in m/s^2


What is force?

Force = mass x acceleration


How does force relate to acceleration?

Force is proportional to acceleration


What is the acceleration of a rocket of mass 50kg and thrust 1200N?

Weight = 50 x 10 = 500N
Overall force = 1200-500 = 700N
Acceleration = 700 ÷ 50 = 14m/s^2


What is terminal velocity?

When acceleration and overall force are both 0


What are the three stages of an object falling?

1) object accelerates downwards due to weight. No drag ∴ overall force downwards
2) as object gains speed, air resistance increases, but weight stays same, so overall force decreases. Acceleration also decreases
3) eventually drag balanced weight, so no overall force or acceleration. Now it has reached terminal velocity.


How can you increase terminal velocity?

Increase the force to increase the acceleration
Make it more streamlined to decease the air resistance


What is thinking time and what can affect it?

Time to react to what you see. Tiredness, visibility, drug/alcohol use, concentration


What is stopping time and what can affect it?

Time between putting foot in break and stopping. Tyres, conditions, breaks, ground


In a distance time graph, what does the gradient represent?



In a velocity time graph, how do you find the distance?

Area enclosed


How do you work out a moment?

Moment(Nm/Ncm) = force x distance


If a person moves from left to right on a bridge, what will happen and why?

The CM will increase, therefore Rr must increase. To do this, Rr's force must increase.


What is Hooke's law?

Force is proportional to extension, as long as elastic limit has not been reached


What are elastic and plastic behaviour?

Elastic = when force removed spring goes back to original length
Plastic = when force removed spring stays a bit stretched


What does a spring's graph tell you?

Straight line through origin ∴ force proportional to extension
F = K x E


What is the spring constant in 2x springs?

In series: 0.5K
In parallel: 2K


What is a force? (newton's 1st law)

That which causes an object to accelerate


What is Newton's third law?

• for every action there is an equal but opposite reaction
∴ for a force to exist there must be two objects. The size of the force on each object will be the same, but they don't cancel out, as act on different objects
E.g. When you jump up the earth has a downward gravitational pull on you of 500N, but you have an upward gravitational pull on the earth of 500N


What is momentum? Is it vector/scalar?

• momentum = mass x velocity
• measured in kgm/s
• vector ∴ direction imp
• you may need to say the direction of the momentum


What is the principle of conservation of momentum?

Total momentum before an action=total momentum after reaction as long as no external forces, e.g. Friction etc.


Wat do you do in explosion problems?

• total m to left = total m to right
• ∴ work out m on one side, then that will be m on other. Therefore you can solve for 1 unknown


What do you do in collision problems?

Subtract the momentum of one object from the momentum of the other object to find the overall m. (remember direction v important)
Then using the PoCoM:
Total mass x velocity = the m you worked out before
Solve for whatever you need to know


What is newton's 2nd law?

Force = change in m /time


How does newton's 2nd law have an effect on car safety/crashes/jumping?

In these cases you want smallest possible force, to avoid injury ∴ as we can't change the initial/final momentum, what we, use do is increase the time taken
We do this by bending knees on impact/crumple zones in cars/airbags


How can changing forces affect speed and direction?

• upwards and downwards forces are balanced
• accelerating: forwards force greater than backwards force
• decelerating: backwards force (drag/friction) greater than forwards force
• direction will travel in whatever direction the force is greatest


How do car safety devices work in relation to momentum?

They try to increase time take for car's/person's momentum to reach 0 ∴ less force on person
• crumple zones crush during a collision ∴ increase time take for m to reach 0
• airbags also increase time for person's momentum to reach 0
• seat belts stop you tumbling around inside and are slightly stretchy ∴ reduce time for m to reach 0