force

Question 1

describe a net force

Answer 1

total force acting on a body, can be balance or unbalanced

Question 2

what is the equation for weight

Answer 2

w = mass x gravity

Question 3

describe what weight is

Answer 3

a vector force that acts vertically downwards from the COM

Question 4

how is reaction force formed

Answer 4

acts from point of contact with the ball

Question 5

define friction

Answer 5

an anti-slipping force which opposed motion and acts when 2 surfaces pass against each other.

Question 6

define air resistance

Answer 6

the force that opposes motion through the air

Question 7

what are the factors affecting friction and give exmaples

Answer 7

• the roughness of the ground surface e.g. rubber track in athletics
• the roughness of the contact surface e.g. spikes in athletics/ studs in football
• the greater the downforce/ mass of an object the greater the friction
• the warmth of the surface

Question 8

what are the facors affecting air resistance

Answer 8

• velocity of moving object
• frontal-cross sectional area
• shape e.g. steamlining helemet
• smoothness of surface

Question 9

define centre of mass

Answer 9

point of balance in a body at which weight appears to act

Question 10

what are the factors affecting centre of mass

Answer 10

• distribution of mass
• movement of the limbs
• unifority of the shape

Question 11

desribe the relationship between COM and stability

Answer 11

• height of COM: lowering COM will increase stability
• position of line of gravity: should be central over the base of support to increase stability
• area of base of support: the more points of contact, the greater the base of suport so the greater the stability
• mass of performer: the greater the mass the more stability due to increased inertia

Question 12

give examples to help explain how a performer could increase stability by lowering centre of mass

Answer 12

• lowering stance in rugby, judo & wrestling makes it harder for opponent to push you over

Question 13

what happens if COM moves near edge of base of support

Answer 13

you will over balance

Question 14

give an example of what happens when COM move near the edge of the base of support

Answer 14

• e.g. a sprinter in the set position will have COM right at edge of base of support
• as they move when they hear the starting pistol they lift their hands off the ground and become off balanced
• this allows the athlete to fall forward & will create the momentum for the speed they require to leave the blocks as quickly as possible