Kinematics
The branch of biomechanics that describes motion without reference to the forces causing it.
Kinematics
Increase the force acting on an object and this happens to its acceleration.
It increases proportionally — Newton's 2nd law, F = ma
The speed of a jet plane that travels 528 m in 4 seconds.
132 m/s
(s = d/t)
Rotation about an axis — a gymnast swinging around the high bar.
Angular motion
The units used to express angular velocity.
Radians per second (rad/s)
A quantity that has both a magnitude and a direction — "5 N to the right."
A vector (a scalar has magnitude only)
The acceleration of an object when all forces acting on it are balanced.
zero
The acceleration of a 10 kg wagon pulled with a force of 2
0.2 m/s²
(a = F/m)
The turning effect produced when a force acts at a distance from an axis of rotation.
Torque
A wrestler widens his stance before contact, increasing this area bounded by his points of contact with the ground.
Base of support
The type of motion a speed skater shows gliding straight down the straightaway.
Linear motion
The law stating that every action force has an equal and opposite reaction force.
Newton's 3rd law
The weight, in newtons, of a 7.26 kg bowling ball.
≈ 71.1 N (7.26 × 9.8)
Decrease the size of a force that does not act through the axis, and this happens to torque.
It decreases (torque = force × perpendicular distance from the axis)
Lowering this point makes an athlete much harder to knock over.
Centre of gravity (centre of mass)
Name both types of motion: a shot put arcing through the air, and a sprinter whose body travels forward while her limbs rotate at the joints.
Curvilinear motion; general motion
You push a cart to the right with 10 N while a friend pushes left with 5 N. Give the net force.
5 N to the right (+10 + −5 = +5 N)
How long a 350 km trip takes at an average speed of 80 km/h.
4.375 hours (4 h 22.5 min)
A body's resistance to a change in its angular motion — depends on mass and how that mass is distributed around the axis.
Moment of Inertia
Cleats, gym chalk and grippy shoes all increase this force between athlete and surface.
Friction
Outline the difference between linear distance and linear displacement.
Distance = total path length covered. Displacement = straight-line change in position from start to finish, with direction
⭐ Double Jeopardy — worth 1000.
Outline the difference between mass and weight.
Mass = quantity of matter, in kg, unchanging. Weight = force of gravity on that mass, in N (mass × 9.8 m/s²)
The net force on an object with a mass of 400 g accelerating at 7.5 m/s².
3 N (convert first — 400 g = 0.4 kg, then 0.4 × 7.5)
A bowling ball spins at an angular velocity of 40.6 rad/s with a moment of inertia of 0.041 kg·m². Give its angular momentum.
A: ≈ 1.66 kg·m²/s (L = I × ω)
⭐ Double Jeopardy — worth 1000.
List four factors that affect an athlete's stability.
Size of the base of support; height of the centre of gravity; position of the line of gravity relative to the base; mass/body weight