P10

Question 1

What is the formula for resultant force?

Answer 1

Resultant force(N)= mass(kg) x acceleration(m/s2)

Question 2

Newton’s second law of motion

Answer 2

The acceleration of an object is:
Proportional to the resultant force on the object
Inversely proportional to the mass of the object
Resultant force = mass x acceleration

Question 3

Inertia

Answer 3

The tendency of an object to stay at rest or continue in uniform motion(constant velocity)

Question 4

What direction is the acceleration in?

Answer 4

Acceleration in same direction as velocity
Velocity increases if resultant force is in the same direction as the velocity(positive acceleration)
Velocity decreases if resultant force is in opposite direction to velocity(negative acceleration)

Question 5

How does mass affect acceleration?

Answer 5

The greater the mass of an object, the smaller its acceleration for a given force

Question 6

What is weight?

Answer 6

The force acting on the object due to gravity - is why an object falls

Question 7

What happens when no forces act on an object?

Answer 7

Resultant force is weight - object has constant acceleration of 9.8m/s2, acceleration due to gravity

Question 8

How do mass and weight change?

Answer 8

Mass stays the same always, at the equator you weigh less than at the poles since gravity is weaker at the equator

Question 9

Mass

Answer 9

Quantity of matter in an object

Question 10

Gravitational field strength

Answer 10

Gravitational force on a 1kg object at a place where the object is

Question 11

Earth’s gravitational field strength at the surface

Answer 11

9.8N/kg

Question 12

Equation for weight

Answer 12

Weight = mass x gravitational field strength(N/kg)

Question 13

Terminal velocity

Answer 13

Constant velocity when frictional force on object is equal and opposite to its weight(maximum velocity on an object)

Question 14

Resultant force on object

Answer 14

Weight minus frictional force

Question 15

What happens to an object when it falls

Answer 15

Acceleration decreases, frictional force increases as it speeds up,resultant force decreases

Question 16

How can you ensure an object in the air can reach constant velocity?

Answer 16

An object can fall further through the air to reach a constant velocity as the frictional force when an object moves through the air is air resistance

Question 17

When an object falls in the fluid

Answer 17

Fluid drags on object due to friction between fluid and surface of moving object, frictional force increases with speed. Object reaches a constant velocity when frictional force is equal and opposite to its weight

Question 18

Object falling in liquid

Answer 18

Two forces are drag force and weight

Question 19

Forces on a car

Answer 19

For any car travelling at a constant velocity, the resultant force is zero, driving force of engine balanced by resistive forces caused by air resistance

Question 20

What affects the braking force

Answer 20

Speed of vehicle when brakes are first applied - greater the speed, greater deceleration to stop vehicle in given distance
Mass - greater the mass, greater the braking force for a given deceleration

Question 21

Thinking distance

Answer 21

Distance travelled by vehicle in time it takes driver to react, directly proportional to speed, thinking distance = speed x reaction time
To do with the brain:
Level of alertness
Drugs/alcohol
Distractions
Speed of vehicle
Mist and fog don’t affect the thinking distance as they don’t affect the brain.

Question 22

Braking distance

Answer 22

Distance travelled by the vehicle during the time the braking force acts
Anything to do with friction between brakes/tyre/road:
Mass of vehicle
Speed of vehicle
State of vehicles’ brakes
Weather
State of the vehicles’ tyres
State of the road(gravel/ice/snow/rain/general condition)
Curve of best fit on graph due to kinetic energy, proportional to v2(speed2)
If you increase the speed, the braking distance increases by speed2:
Doubling the speed quadruples the braking distance
Tripling the speed increases the braking distance by 9 times

Question 23

Stopping distance

Answer 23

Thinking distance + braking distance, shortest distance a vehicle can stop in, how far a vehicle will travel between the moment it brakes and the moment it comes to a complete stoo

Question 24

Factors affecting stopping distances

Answer 24

Tiredness, alcohol, drugs and mobile phones(distractions) increase reaction time and thinking distance, so increase stopping distance
Thinking distance and braking distance increase with increased speed
In adverse road conditions, drivers brake with less force to avoid skidding, stopping distances greater in poor weather + road conditions
Poorly maintained vehicles with ineffective brakes and tyres take longer to stop

Question 25

Deceleration

Answer 25

a = -u2/2s where u= initial speed s = distance travelled

Question 26

Deceleration to avoid skidding on a dry flat road

Answer 26

No more than 6m/s2

Question 27

Forces needed to accelerate a road vehicle

Answer 27

6KN-250KN

Question 28

Momentum

Answer 28

Momentum(kg m/s)= mass x velocity, a vector quantity

Question 29

Conservation of momentum

Answer 29

In a closed system, momentum same before and after an event as long as there are no external forces

Question 30

Elastic objects

Answer 30

If they return to their original shape after the forces deforming it are removed(elastically deformed objects), squash ball, rubber band

Question 31

Extension

Answer 31

Length at stage - original length

Question 32

Hooke's Law

Answer 32

The extension of a spring is directly proportional to the force applied as long as the limit of proportionality isn't exceeded(when spring stretches more than predicred) Rubber and polythene have a non-linear relationship between their extension and force(low limit of proportionality) Steel spring has higher limit of priportionality Force applied = spring constant(N/m) x extension Applies to a compressed object, change of length is a compression, not an extension

Question 33

Acceleration on moon

Answer 33

Lower acceleration due to no air resistance and no atmosphere

Question 34

Being streamlined

Answer 34

Streamlined(aerodynamic, smaller surface area), the more streamlined you are, the faster the terminal velocity

Question 35

Parachute

Answer 35

1.Hanging from the leg of a helicopter - Weight is equal to tension, no acceleration, balanced forces, terminal velocity 2. Person falling from plane - Weight stays the same, air resistance increases as you fall, big acceleration due to difference between weight + air resistance 3) Air resistance and weight balanced forces, no acceleration 4)Pulling the shoot- Increasing air resistance due to larger surface area, same weight, unbalanced forces so big deceleration 5)After pulling the shoot - Terminal velocity, air resistance = weight, falling out at a constant speed, balanced forces, slows down so air resistance reduced

Question 36

Is gravity a force?

Answer 36

NO!

Question 37

Gravity

Answer 37

Acceleration of an object due to the Earth's mass, the weakest of the fundamental forces

Question 38

What happens to two objects of equal mass

Answer 38

They hit the floor at the same time due to equal amounts of graviy acting on them and equal amounts of air resistance acting in them

Question 39

Acceleration in a vacuum

Answer 39

In a vacuum, there is no air, so the object continues to accelerate

Question 40

How does gravitational force affect size

Answer 40

Planets with a similar gravitational force have a similar size

Question 41

How does mass affect the gravitational force?

Answer 41

Objects without mass - no gravitational force Objects with mass - gravitational force

Question 42

Forces on orbiting objects

Answer 42

There are unbalanced forces on orbiting objects, with only the gravitational force acting, since the object accelerates. If you are orbiting, you are weightless as you feel you're always falling, there is little gravity

Question 43

Forces on unorbiting objects

Answer 43

If you're next to something like the sun without orbiting, you have weight as you're pulled by the gravitational force of the sun

Question 44

What is an object's weight in deep space?

Answer 44

An object is weightless in deep space, but its mass doesn't change

Question 45

Does mass affect the acceleration when an object falls?

Answer 45

No, because the force could be the weight: acceleration = gravity

Question 46

What affects how far a car goes before it stops

Answer 46

Momentum(mass + velocity of a car) Friction in tyres Quality of road Drugs Tiredness Brake pads Type of brakes

Question 47

How does mass affect momentum?

Answer 47

The bigger the mass, the more momentum + force needed to stop an object

Question 48

Momentum experiment

Answer 48

You could change the height of a slope when trying to test momentum with one block at the end, measure how much block moves. Measure speed near the end of a ramp.