# P10

What does Newton's second law of motion say?
Proportional to the resultant force on the object, inversely proportional to mass of object
1 of 34
What is inertia?
The tendency of an object to stay at rest or to continue in uniform motion
2 of 34
What is needed to change the velocity of an object?
A resultant force
3 of 34
What happens if the velocity of an object changes?
It must be acted on by a resultant force
4 of 34
What happens if the velocity of an object increases?
Resultant force in same direction as velocity, acceleration is positive
5 of 34
What happens if the velocity of an object decreases?
If resultant force in opposite you say acceleration is negative
6 of 34
What is weight?
Force acting on it due to gravity
7 of 34
What is mass?
Quantity of matter in it
8 of 34
What happens if an object falls in fluid?
The fluid drags on the object because of fluid between fluid and object
9 of 34
Why does the acceleration of an object decrease as it falls?
Frictional force increases as it speeds up so resultant force decreases and so does acceleration
10 of 34
When does an object reach a constant velocity?
When frictional force on it is equal and opposite to its weight
11 of 34
What is that velocity called?
Terminal velocity- when resultant = 0 and acceleration = 0
12 of 34
What does braking force of a vehicle depend on?
Speed of car and mass of car
13 of 34
What is the relationship between speed and braking force?
Higher the speed higher the braking force same with mass of car
14 of 34
What is stopping distance?
Shortest distance a vehicle can safely stop in
15 of 34
What is thinking distance?
The distance travelled by the vehicle in time for driver to react
16 of 34
What is braking distance?
Distance travelled by vehicle during time braking force acts
17 of 34
What is the formula for stopping distance?
Thinking distance + braking distance
18 of 34
What is the equation for deceleration?
Same as acceleration but with a -
19 of 34
What affect reaction times which effects stopping distance?
Tiredness, drugs, alcohol and mobile phones
20 of 34
How does weather affect stopping distance?
Icy and slippy roads cause braking with less force
21 of 34
How does poorly maintained vehicles affect stopping distance?
Can take longer to break as is less effective
22 of 34
What is the law of conservation of momentum?
In a closed system the total momentum before an event is equal to the total momentum after
23 of 34
What happens if an impact time is longer?
The more the impact force is reduced
24 of 34
What happens when two vehicles collide?
They exert equal and opposite forces and their total momentum is unchanged
25 of 34
What is the equation for impact force?
Change of momentum/ impact time
26 of 34
What is the point in a helmet?
It increases impact time
27 of 34
What is the point of a seatbelt?
It decreases decelerating force
28 of 34
Why does the seatbelt go across the chest?
29 of 34
What do airbags do?
Spread force of impact across upper part of body, increases impact time
30 of 34
What is a crumple zone?
The structural safety feature that absorbs energy
31 of 34
What is the point of cushioned surfaces?
They increase impact time and impact force reduced
32 of 34
How to know if an object is elastic?
It returns to original shape when force deforming it is removed
33 of 34
What is Hookes law?
The extension of a spring is directly proportional to the force applied
34 of 34

## Other cards in this set

### Card 2

What is inertia?

#### Back

The tendency of an object to stay at rest or to continue in uniform motion

### Card 3

#### Front

What is needed to change the velocity of an object?

### Card 4

#### Front

What happens if the velocity of an object changes?

### Card 5

#### Front

What happens if the velocity of an object increases?