Laws of motion

Question 1

1st law

Answer 1

An object at rest tends to stay at rest and an object in motion tends to stay in motions at a constant speed along a straight-line path, unless an outside net force is placed upon it.

Question 2

Inertia

Answer 2

Property of objects to resist changes in motion

Question 3

Net force

Answer 3

When more than a single force acts on an object

Question 4

Force

Answer 4

Push or pull

• gravitational, electrical, magnetic, muscular
• lbs and newtons

Question 5

Vector quantity

Answer 5

A quantity such a as force that has both magnitude and direction

Question 6

Mechanical equilibrium

Answer 6

When the net force on something is zero
- vector sum of forces equals zero
(Upward forces are + and downward forces are -)

Question 7

Support force

Answer 7

Normal force

- upward force opposite to the force of gravity

Question 8

Dynamic equilibrium

Answer 8

An object moving at a constant speed in a straight-line path is also in equilibrium

Question 9

Equilibrium

Answer 9

State of no change (must be 2+ forces acting on object; cannot just be 1)

Question 10

Linear motion

Answer 10

The simplest motion is the simplest form of motion (straight line path)

Question 11

Speed =

Answer 11

Distance covered per unit of time

Speed = distance / time

Question 12

Instantaneous speed

Answer 12

Speed at any instant in time

Question 13

Average speed

Answer 13

Total distance covered / time interval

- does not indicate different speeds and variations that may take place during shorter time intervals

Question 14

Velocity

Answer 14

Linear motion

- description of how fast and in what direction an object is moving

Question 15

Vector quantity

Answer 15

Quantity that specifies direction as well as magnitude (such as velocity and force)

Question 16

Constant velocity

Answer 16

Motion in a straight line at a constant speed

- must have constant speed and constant direction

Question 17

Changing velocity

Answer 17

Either the speed or the direction (or both) change

Question 18

Acceleration

Answer 18

How quickly velocity changes
a = change in velocity / time
- acceleration is not just the total change in velocity. It is the time rate of change, or change per second in velocity

Question 19

Acceleration in a curve?

Answer 19

Accelerate whenever we move in a curved path (even if we are moving at a constant speed) because our direction is changing

Question 20

Free fall

Answer 20

Lack of gravity. 10 m/s2

Question 21

G on earth

Answer 21

9.8 m/s2

Question 22

V = gt

Answer 22

Instantaneous velocity of an object falling from rest after a time

Question 23

Distance =

Answer 23

1/2 a(t2)

Question 24

Distance in free fall =

Answer 24

1/2 g(t2)

Question 25

Remember

Answer 25

1. How fast: v = gt 2. How far: d = 1/2gt2 3. Acceleration is not a velocity, it is the rate at which velocity itself changes

Question 26

Newton’s 2nd law of motion

Answer 26

When a force acts on an object, the object will accelerate | F = ma

Question 27

Units of F, m, and a

Answer 27

``` F = newtons (N) M = kg A = m/s2 ```

Question 28

Cause of acceleration

Answer 28

Is net force. An object’s acceleration is directly proportional to the force acting on it

Question 29

Friction

Answer 29

1. Forced produced when surfaces are sliding over one another 2. Usually reduces the net force and the resulting acceleration 3. The direction of force is always in a direction opposing motion 4. Zero net force results in zero acceleration and constant velocity 5. Fluid friction (air resistance)

Question 30

Friction does not depend on

Answer 30

5. Does not depend on speed. (May be more when an object is at rest and on the verge of sliding, but once sliding it remains constant) 6. Area of contact

Question 31

Mass

Answer 31

Amount of matter in an object. Measure of the inertia of a material object

Question 32

Weight

Answer 32

Force upon an object due to gravity

Question 33

Free fall

Answer 33

- ration of weight to mass for freely falling objects = a constant (g) - acceleration of free fall is independent of an objects’s mass

Question 34

Non free fall

Answer 34

Acceleration is less than g | - air drag depends on frontal area of falling object and speed of the falling object.

Question 35

Terminal speed

Answer 35

When acceleration terminates (during non free fall)

Question 36

Acceleration =

Answer 36

A = (mg-R)/m

Question 37

3rd law of motion

Answer 37

When an object exerts a force on a second object, the second object exerts an equal and opposite reaction.

Question 38

Action and reaction

Answer 38

- always occur simultaneously and act on different objects | - neither force exists without the other

Question 39

Lift

Answer 39

The upward reaction force caused when air particles are forced down (action) and the air forces the object up (reaction)

Question 40

Vector quantity

Answer 40

Any quantity that requires both magnitude and direction for a complete description (force, velocty, acceleration)

Question 41

Scalar quantity

Answer 41

A quantity that can be described by magnitude only (no direction involved) (mass, volume, speed)

Question 42

Vector

Answer 42

An arrow that represents a vector quantity - length is scaled to represent the magnitude, the direction shows the direction of the quantity

Question 43

Resultant

Answer 43

Sum of 2+ vectors

Question 44

Parallelogram rule

Answer 44

Construct a parallelogram whereinthe two vectors are adjacent sides, the diagonal will show the resultant