TOPIC FOUR - Mechanics

Question 1

what does the area of a velocity-time graph show?

Answer 1

distance travelled

Question 2

what does the gradient of a velocity-time graph show?

Answer 2

acceleration

Question 3

what does the area of an acceleration-time graph show?

Answer 3

change in velocity

Question 4

what does the gradient of a displacement-time graph show?

Answer 4

velocity

Question 5

what does the area of a force-time graph show?

Answer 5

change in momentum

Question 6

what does the area of a force-distance graph show?

Answer 6

workdone

Question 7

what is newtons 1st law?

Answer 7

an object will remain at rest or constant velocity unless acted on by an external force

Question 8

what is newtons second law?

Answer 8

the rate of change of momentum is directly proportional to the resultant external force

Question 9

what is newtons 3rd law?

Answer 9

when body A exerts a force on body B, body B exerts an equal but opposite force on body A

Question 10

what is the definition of a moment?

Answer 10

force x perpendicular distance from the point of the line of action of the force

Question 11

what is the principle of moments?

Answer 11

the sum of anticlockwise moments = the sum of the clockwise moments

Question 12

what is a couple?

Answer 12

a pair of equal forces acting in opposite directions

Question 13

what is torque? and equation?

Answer 13

torque = the moment of a couple
torque = force x perpendicular distance from the point of the line of action of the force

Question 14

what is thinking distance? what is its equation?

Answer 14

• distance travelled in the time taken to react
• s1 = speed x reaction time
  s1 = ut

Question 15

what is braking distance? what is its equation?

Answer 15

• distance travelled in time taken to stop safely from when brakes are first applied
• s2 = u^2/2a

Question 16

what is stopping distance?

Answer 16

thinking distance + braking distance

ut + u^2/2a

Question 17

how do bumpers help?

Answer 17

increase impact time = decrease impact force

Question 18

how do crumple zones help?

Answer 18

increase impact time = decrease impact force

Question 19

how do seat belts help?

Answer 19

they have a restraining force which is less than the impact force

Question 20

how do collapsible steering wheels help?

Answer 20

decrease impact force

Question 21

how do airbags help?

Answer 21

increase impact time = decrease impact force

spread contact area

Question 22

what are the 5 safety features in cars?

Answer 22

• bumpers
• crumple zones
• seat belts
• collapsible steering wheels
• airbags

Question 23

what is motive force?

Answer 23

force provided by an engine

Question 24

what is terminal velocity?

Answer 24

max speed when resistive force = driving force

Question 25

what does the law of conservation of momentum state?

Answer 25

momentum before = momentum after

Question 26

what is the difference between elastic and inelastic collisions?

Answer 26

ELASTIC - Ek is conserved | INELASTIC - Ek is not conserved

Question 27

what is power output?

Answer 27

rate of doing work

Question 28

how do you derive P = Fv

Answer 28

P = W/t = F x s /t = F v