p2 - forces (from PMT)

Question 1

define a force

Answer 1

a push or pull acting on an object due to an interaction with another object

Question 2

what is the name given to the single force that is equivalent to all the other forces acting on a given object?

Answer 2

the resultant force

Question 3

define inertia

Answer 3

an object’s resistance to motion

Question 4

define inertial mass

Answer 4

-a measure of how difficult it is to change a given object’s velocity
-the ratio of force over acceleration

Question 5

explain how a seatbelt improves a passenger’s safety during a collision

Answer 5

-passenger has to decelerate from the vehicle’s velocity at impact to zero, so they experience force
-force is equal to the rate of change of momentum
-seatbelts increase the time over which the force is applied, reducing the rate of change of momentum and therefore reducing the forced felt by the passenger

Question 6

what quantity is equal to the force experienced in a collision?

Answer 6

the rate of change of momentum

Question 7

what does it mean if a force is said to do ‘work’?

Answer 7

the force cause an object to be displaced through a distance

Question 8

define power

Answer 8

the rate at which work is done

Question 9

at what point does hooke’s law no longer apply?

Answer 9

the limit of proportionality

Question 10

what is weight

Answer 10

the force that acts on an object due to gravity and the object’s mass

Question 11

what is meant by an object’s centre of mass?

Answer 11

the single point through which an object’s weight can be considered to act through

Question 12

what is the acceleration of an object falling in free fall with no resistive forces acting?

Answer 12

10m/s^2

Question 13

what is the alternative name for the turning effect of a force?

Answer 13

a moment

Question 14

what distance measurement is used when calculating a moment?

Answer 14

the perpendicular distance from the pivot to the line of action of the force

Question 15

if an object is in equilibrium, what can be said about the moments acting on the object?

Answer 15

the clockwise moments are equal to the anticlockwise moments

Question 16

what does the direction of a resultant moment acting on an object tell you?

Answer 16

the direction that the object will rotate around the pivot point

Question 17

in any fluid, at what angle do the forces due to pressure act on a given surface?

Answer 17

at right angles (normal to) the surface

Question 18

what can be said about the pressure in a simple hydraulic system?

Answer 18

the pressure in the fluid is constant through the fluid

Question 19

explain how a simple hydraulic lift works

Answer 19

-pressure is constant in the fluid
-force is applied on each platform is equal to the product of pressure and area (F=pA)
-one platform has a larger area than the other, meaning that the force produced is greater than the force applied to the smaller platform