P2.3 (1) - forces in action Flashcards Preview

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Flashcards in P2.3 (1) - forces in action Deck (34)
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1
Q

what are elastic bodies?

A

objects that return to original shapes when the deforming force is removed

2
Q

what are plastic bodies?

A

objects that do not return to their original shape when the deforming force is removed

3
Q

state hooke’s law

A

the extension of a body is directly proportional to the force applied, as long as the limit of proportionality is not exceeded

4
Q

what is the equation for hooke’s law?

A
force = spring constant x extension 
(N)    =     (N/m)                 x  (m)

F = K x E

5
Q

how can the spring constant be found from a force-extension graph?

A

from the gradient

6
Q

where does the limit of proportionality lie on an extension-force graph?

A

just before it begins to curve

7
Q

what is the elastic limit?

A

the like middle point

  • if exceeded, spring is permanently deformed (even when force is removed)
  • below limit, spring returns to original length
8
Q

where is the elastic limit on a force-extension graph?

A

just after the limit of proportionality

9
Q

what is the spring constant a measure of?

A

the stiffness of a spring

10
Q

if a spring is very stiff, how is the spring constant?

A

higher

11
Q

what is the equation to figure out the work done while stretching a spring?

A

energy (J) = 0.5 x spring constant (N/m) x (extension (m))^2

12
Q

what is the work done while stretching a spring also known as?

A

elastic potential energy

13
Q

can you use an elastic band instead of a spring when using a newton-meter, and why?

A

no, as it does not obey Hooke’s law (as it has a non-linear relationship between force and extension)

14
Q

why is a rubber balloon hard to blow up at first (picture graph in your head)?

A

as rubber does not follow hooke’s law.

so at the beginning the gradient is very high, meaning more force is applied to increase its extension

15
Q

describe the relationship between glass and force and extension

A

it has a linear relationship (straight line), but a very steep gradient - as it is a stiff material

16
Q

what prevents tennis rackets from being deformed when hitting a tennis ball?

A

they are specially designed to transfer energy back, rather than storing them when they deform

17
Q

what causes materials to deform?

A

storing too much energy

18
Q

what is elastic potential energy?

A

energy stored by an elastic body (that has been stretched)

19
Q

how is a rubber band able to revert back to its original shape when the force is released? (energy)

A

converts elastic potential energy to kinetic energy (and so it moves)

20
Q

define a field

A

a region of space within which a body experiences a force

21
Q

where would you find a gravitational field?

A

around anything with mass (infinite)

22
Q

where would you find a magnetic field?

A

around any magnet

23
Q

where would you find an electrostatic field?

A

around anything that is charged

24
Q

do fields exert the same force on every body?

A

no, it depends on how much mass/charge/magnetism the body itself has

25
Q

what is the unit for gravity?

A

n/kg

26
Q

what is weight?

A

The force of the Earth on an object (acts downwards)

27
Q

what is gravitational field strength a measure of?

A

the force on 1kg of mass in a gravitational field (due to another mass)

28
Q

what is the equation to calculate gravity constant?

A

mass x gravitational field strength

29
Q

what is gravitational potential energy?

A

The energy transferred to a gravity store when you lift an object in a gravitational field

30
Q

equation for calculating gravitational potential energy

A

(J) = mass (kg) x height (m) x gravitational field strength (N/kg)

31
Q

what has to be present to stretch, bend or compress an object?

A

more than one force must be present + applied

32
Q

what is the difference between linear and non-linear relationship between force and extension?

A

linear relationships obey hooke’s law, non-linear relationships do not obey hooke’s law

33
Q

how would a gravitational field differ with mass?

A

greater the mass, greater the gravitational field around it

34
Q

what is the acceleration in free fall?

A

10m/s^2