Forces And Their Effects 3.1

Question 1

Non-contact forces?

Answer 1

Objects interact by non-contact (field) forces (including gravity, electrostatics, magnetism)

Question 2

Contact forces?

Answer 2

and by contact forces (including friction, air resistance, tension and normal contact force).

Question 3

What is friction?

Answer 3

Friction is a force between two surfaces, which impedes motion and may result in heating.

Question 4

What is air resistance?

Answer 4

Air resistance is a form of friction.

Question 5

How can vectors be represented?

Answer 5

Pairs of objects interact to produce a force on each other, which can be represented as vectors.

Question 6

What are scalars

Answer 6

Scalars are quantities that have magnitude only.

Question 7

What are vectors?

Answer 7

Vectors are quantities that have direction as well as a magnitude.

Question 8

How can a vector quantity be represented?

Answer 8

A vector quantity may be represented by an arrow. The length of the arrow represents the magnitude and the direction of the arrow represents the direction of the vector quantity.

Question 9

Scalar examples?

Answer 9

distance, speed and time

Question 10

Vector examples?

Answer 10

displacement, velocity,acceleration, force and momentum

Question 11

What is weight and what does it depend on?

Answer 11

Weight is the force acting on an object due to gravity. The weight of an object depends on the gravitational field strength at the point where the object is.

The weight of an object can be calculated using the equation:
Weight (N) = mass (kg) × gravitational field strength (N/kg)
W = m × 8

Question 12

What happens when more than one force is applied to an object?

Answer 12

When more than one force is applied to an object they may cause a change in the shape of the object, by stretching, bending or compressing.

Question 13

What happens after elastic distortions?

Answer 13

After elastic distortions an object returns to its original shape when the forces are removed.

Question 14

What happens after inelastic distortions?

Answer 14

After inelastic distortions an object does not return to its original shape.

Question 15

What happens when a force is applied to an elastic object (such as a spring)?

Answer 15

A force applied to an elastic object such as a spring will result in the object stretching and storing elastic potential energy.

Question 16

When an object is behaving elastically..

Answer 16

For an object behaving elastically, the extension is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.

The relationship between the force, F, and the extension, e, is:
F=kx e
where k is a constant.

Question 17

How can an objects distance be represented on a distance-time graph?

Answer 17

If an object moves in a straight line, its distance from a certain point can be represented by a distance-time graph.

Question 18

How can the speed of an object be calculated from a distance-time graph?

Answer 18

The speed of the object can be calculated from the gradient of a distance-time graph.

Question 19

Velocity of on object? calculation?

Answer 19

The velocity, v, of an object is its speed in a given direction and is given by the equation: v=s/t
where s is the displacement and t is the time taken.
This equation can also be used to calculate the average speed of objects undergoing non-uniform motion.

Question 20

Newton’s third law?

Answer 20

Whenever two objects interact, the forces they exert on each other are equal in magnitude and opposite in direction. This is Newton’s Third Law.

Question 21

Resultant force? Effect on object?

Answer 21

A number of forces acting on an object may be replaced by a single force that has the same effect on the
motion as all the original forces acting together. This single force is called the resultant force.

Question 22

What effect does A non-zero resultant force acting on an object have?

Answer 22

A non-zero resultant force acting on an object causes it to accelerate.

Question 23

What is acceleration and how can an object accelerate?

Answer 23

Acceleration is the rate of change of velocity. An object can accelerate by changing its direction even if it Is going at a constant speed.

Question 24

Negative acceleration?

Answer 24

Deceleration

Question 25

How can acceleration be calculated?

Answer 25

The average acceleration, a, of an object is given by the equation:
A=/\v/t
where A/\is the change in velocity and t is the time taken for the object to accelerate

Question 26

How can the acceleration of an object be calculated from a velocity-time graph?

Answer 26

The acceleration of an object can be calculated from the gradient of the velocity-time graph.

Question 27

How can the distance travelled by an object be calculated from a velocity-time graph?

Answer 27

The distance travelled by an object can be calculated from the area under a velocity-time graph

Question 28

Newton’s first law?

Answer 28

If the resultant force acting on an object is zero:
-a moving object will continue to move at the same velocity
-a stationary object will remain at rest
This is Newton’s First Law.

Question 29

Calculation for newtons second law?

Answer 29

if the resultant force on an obiect is not zero. the object will accelerate in the direction of the resultant force
The relationship between the resultant force, I, acting on an object, its mass, m, and the acceleration caused a, is:
F=mxa
This is Newton’s Second Law.

Question 30

Momentum?

Answer 30

All moving objects have momentum. The relationship between momentum, p, mass, m, and velocity, v, is:
p=mXv

Question 31

conservation of momentum?

Answer 31

In a closed system the total momentum before an interaction is equal to the total momentum after the Interaction. This is called conservation of momentum.

Question 32

What happens when a vehicle travels at a steady speed in a straight line ?

Answer 32

When a vehicle travels at a steady speed in a straight line the resistive forces are balancing the driving force.

Question 33

The greater the speed of a vehicle the…

Answer 33

The greater the speed of a vehicle the greater the braking force needed to stop it in a certain distance.

Question 34

The greater the braking force the..

Answer 34

The greater the braking force the greater the deceleration of the vehicle.

Question 35

Large decelerations may lead to..

Answer 35

Large decelerations may lead to brakes overheating and/or loss or control.

Question 36

for a given braking force, the greater the speed, the greater the..

Answer 36

stopping distance.

Question 37

Stopping distance?

Answer 37

The stopping distance of a vehicle is the sum of the thinking distance and the braking distance combined

Question 38

Thinking distance?

Answer 38

the distance the vehicle travels during the driver’s reaction time is the thinking distance.

Question 39

Braking distance?

Answer 39

the distance it travels under the braking force is the braking distance

Question 40

What can affect a driver’s reaction time?

Answer 40

A driver’s reaction time can be affected by tiredness, distractions, drugs and alcohol.

Question 41

What happens When the brakes of a vehicle are applied?

Answer 41

When the brakes of a vehicle are applied, work done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle and the temperature of the brakes increases.

Question 42

How can a vehicles braking distance be affected?

Answer 42

A vehicle’s braking distance can be affected by adverse road and weather conditions and poor condition of the
vehicle.
Students should understand that ‘adverse road conditions includes wet or icy conditions. Poor condition of the car is limited to the car’s brakes or tyres.

Question 43

What happens when an object moves through a fluid?

Answer 43

An object moving through a fluid experiences friction. The faster the object moves, the greater the frictional forces (drag) acting on it.

Question 44

What happens when an object falls through a fluid?

Answer 44

An object falling through a fluid will initially accelerate due to the force of gravity and the drag forces increase as the velocity increases. Eventually the resultant force will be zero and the object will move at its terminal velocity.

Question 45

What are parachutes designed for?

Answer 45

Parachutes are designed to increase the drag force on a parachutist so that the terminal velocity is reduced

Question 46

What is the purpose of streamlining?

Answer 46

Streamlining reduces the drag force on an object so that its maximum velocity is increased.

Question 47

What is the centre of mass of an object?

Answer 47

The centre of mass of an object is the point at which the mass of the object may be thought to be concentrated

Question 48

What happens if an object is freely suspended?

Answer 48

If freely suspended, an object will come to rest with its centre of mass directly below the point of suspension.

Question 49

Symmetrical object’s central mass ?

Answer 49

The centre of mass of a symmetrical object is along the axis of symmetry. The position of the centre of mass affects the stability of objects.

Question 50

What is a moment?

Answer 50

The turning effect of a force is called a moment

Question 51

What should be done if an object is not turning?

Answer 51

If an object is not turning, the total clockwise moment must be exactly balanced by the total anti-clockwise moment about any pivot

Question 52

What happens If the line of action of the weight of an object lies outside the base of the object?

Answer 52

If the line of action of the weight of an object lies outside the base of the object there will be a resultant moment and the body will topple.

Question 53

What can be used as force multipliers?

Answer 53

Simple levers can be used as force multipliers.