A2 PE Mechanics of Movement

Question 0

What is a scalar?

Answer 0

A quantity which only has a magnitude (size)

Speed, distance and mass are scalar quantities.

Question 1

Linear motion is…

Answer 1

Movement of a body in a straight line where all parts are moving in the same direction at the same speed.

Question 2

What is a vector?

Answer 2

A quantity that has both a direction and a magnitude (size).
Velocity, acceleration, momentum are all vectors.
It is demonstrated by an arrow which points in the direction of travel and is a length that represents the size of the force.

Question 3

Speed =

Answer 3

Distance/time

Units are ms

Question 4

Velocity =

Answer 4

Displacement / time (units are ms)

Question 5

The amount of ground covered during motion is …

Answer 5

Distance (units are m)

Question 6

How would you calculate displacement?

Answer 6

Straight line length from starting point to finishing point. (Units are m)

Question 7

Acceleration =

Answer 7

Change in velocity/time

Vf-Vi/ time

(Units are ms)

Question 8

Force =

Answer 8

Mass x acceleration.

E.g Weight = mass x gravity

Question 9

Momentum =

Answer 9

Mass x velocity (units are kgms)

Question 10

Impulse =

Answer 10

Force x time (units are ft)

Question 11

When an athlete is RUNNING, the curve you would draw on an impulse graph always starts below the line, true or false?

Answer 11

True - this is the negative force applied when the sprinter lands on the track.

When a performer is leaving the blocks the force is totally above the line - they haven’t landed on the track yet.

Question 12

When drawing an impulse graph for a sprinter who is moving at constant velocity, what would the graph look like?

Answer 12

A symmetrical ‘S’ shape where the negative force below the x axis is the same size and shape as the positive force above the x axis.

Question 13

Name Newton’s first law, explain it and give and example.

Answer 13

INERTIA
A body continues in a state of rest or constant velocity unless acted upon by an external force.
E.g a swimmer will stay on the blocks until they contract their muscles to apply a force.

Question 14

Name Newton’s second law, describe it and give an example.

Answer 14

ACCELERATION (force = mass x acceleration)
When a force acts on an object, the rate of change of velocity experienced by the object is proportional to the size of the force and travels in the direction the force is applied.
E.g the force used by a sprinter pushing off the starting blocks is equal to the force they will accelerate with in the opposite direction

Question 15

Name Newton’s third law, describe it and give an example.

Answer 15

ACTION AND REACTION
For every action there is an equal and opposite reaction (ground reaction force)
E.g if a high jumper applies a force into the ground they will receive and equal and opposite force to allow them to jump into the air.

Question 16

Forces are any push or pull which cause a change in velocity, what four things can forces do?

Answer 16

1. Cause a body to move
2. Cause a body to accelerate and decelerate
3. Cause a body to change direction
4. Cause a body to change shape

Question 17

Give 3 examples of horizontal forces

Answer 17

Friction
Air resistance
Drag

Question 18

Give three examples of vertical forces.

Answer 18

Gravity (9.8ms)
Weight force (mass x gravity)
Ground reaction force (from Newton’s 3rd law)

Question 19

What is the name of the trajectory of an object in flight?

Answer 19

Parabola

Question 20

What vertical force acts on a projectile while it is in the air?

Answer 20

Gravity

Question 21

Which component of a parabola does gravity affect?

Answer 21

The vertical component - it causes the object to accelerate downwards when it is in flight. This causes the symmetrical ‘inverted U’ shape of the parabola.

Question 22

What effect does air resistance have on a projectile like a person doing the long jump?

Answer 22

Very little as the mass of the performer is large.

It would affect the horizontal component, but it’s effect is considered to be ‘negligible’.

Question 23

Give 3 factors that affect horizontal displacement of a projectile (how far the projectile travels)

Answer 23

Height of release
Velocity / speed of release
Angle of release

Question 24

The horizontal component of a projectile like a shot put stays the same throughout flight, true or false?

Answer 24

True, the ‘speed’ of release will determine the horizontal component (momentum = mass x velocity).

The shot would continue to move with constant velocity until another force acts upon it (Newton’s first law)

Question 25

What is angular momentum?

Answer 25

Angular velocity x moment of inertia

It remains constant when a rotating object is in flight

Question 26

What is angular velocity?

Answer 26

The rate at which an object or body spins (speed of spin)

Question 27

What is the moment of inertia?

Answer 27

Distribution of mass from the axis of rotation;
As it increases, angular velocity decreases (slower spin)
As it decreases, angular velocity increases (faster spin)

Question 28

How does the mass of an object affect moment of inertia?

Answer 28

The greater the mass the greater the moment of inertia.

A bowling ball has a higher moment of inertia than a volleyball so will require more force to roll it along the ground.

Question 29

How can a performer use their moment of inertia to increase or decrease their angular velocity (speed of rotation)?

Answer 29

Speed up= decrease their moment of inertia- tucking limbs

Slow down= increase their moment of inertia- extending limbs

Question 30

Are moment of inertial and angular velocity A) directly proportional or B) inversely proportional?

Answer 30

B) inversely proportional. As one increases the other decreases.

As the rate of spin (angular velocity) of a body INCREASES, moment of inertia (distribution of mass from axis of rotation) has to DECREASE.