P9/10 : Motion and Braking

Question 1

what is a moment? and equn?

Answer 1

turning effect of force about a point
M= FD

Question 2

How do u increase the moment?

Answer 2

• increase perpendicular distance of pivot
• increase size of force

Question 3

priniciple of momemts ?

Answer 3

total anticlockwise moment=total clockwise moment

Question 4

what is a lever and how can u make them work better?

Answer 4

A solid bar turning on a pivot
works better if:
- increase size of force
- increase distance of force from pivot

Question 5

what do GEARS do ?

Answer 5

multiply effect of turning force using moments

Question 6

why is the moment of each gear NOT the same?

Answer 6

bc it depends on the SIZE of the gear - distance from pivot is larger in larger gear

Question 7

what is compression, stretching and bending?

Answer 7

COMPRESSION : forces act towards eachother
STRETCHING : forces are away from eachother due to NEWTONS THIRD LAW
BENDING : forces act towards eachother, but at different points on the object

Question 8

what is hooke’s law? eqn?

Answer 8

extension of object is directly proportional to force applied
f= ke

Question 9

what is diplacement?

Answer 9

measure of how far somethng is from starting position, along with its direction

Question 10

what is speed of walking, sound, running, cycling?

Answer 10

1.5m/s
330m/s
3m/s
6m/s

Question 11

how do lightgates work?

Answer 11

a flag on top of moving object blocks a beam of light - triggers TIMER
- second light gate used to stop timer as it passes through it

timer measures how long light was blocked for
distance is given by length of flag

Question 12

why is velocity changing in a circular motion?

Answer 12

speed is constant , but direction is changing

Question 13

what equn links acceleration and velocity?

Answer 13

acceleration = velocity/time

Question 14

equn for resultant force?

Answer 14

mass x acceleration

Question 15

define

stopping distance? and equn?

Answer 15

total distance travelled during the time for a car to stop in response to some emergency

stopping d. = thinking d. + braking d.

Question 16

define

thinking distance? equn?

Answer 16

distance travelled by a car when driver realised they need to brake to when they apply the brakes

thinking d. = speed of car x driver’s reaction time

Question 17

factors effecting thinking distance?

Answer 17

• tiredness
• distraction
• intoxication

Question 18

define

braking distance? and factors effecting this?

Answer 18

distance travelled by car under braking force
factor effecting this:
- vehicle condition
- road condition
- vehicle mass

Question 19

work done by brakes equn?

Answer 19

braking FORCE x braking DISTANCE = 1/2 mv^2
braking d. is propertional to vehicle’s speed

Question 20

momentum of object equn?

Answer 20

momentum = mass x velocity
p = mv

Question 21

conservation fo momentum principle?

Answer 21

in a closed system, the total momentum before an event is equal to the total momentum after the event

Question 22

How do protective pads help reduce injury when player collide?

Answer 22

• increase time for players to stop
• so rate of change of momentum is decreased
• decreasing force exerted
  f=m/t