FORCES AND MOTION

Question 1

Definition of Displacement

Answer 1

The distance of an object from a fixed point in a specified direction.

Question 2

Definition of Velocity

Answer 2

The rate of change of displacement.

Question 3

Definition of Acceleration

Answer 3

The rate of change of velocity.

Question 4

Equation linking speed, distance and time

Answer 4

Speed = Distance/Time

Question 5

Gradient of distance time graph and curved lines

Answer 5

Gradient = Velocity
Curved lines = Acceleration

Question 6

Definition of braking distance

Answer 6

The distance travelled between the brakes being applied and the vehicle coming to stop.
- Affected by road conditions and vehicle

Question 7

Definition of free fall

Answer 7

An object is Said to be in free Fall when the only force acting on it is the force of gravity

Question 8

Definition of Instantaneous speed

Answer 8

The exact speed of an object at a specific given point

Question 9

Definition of thinking distance

Answer 9

Distance travelled in the time it takes for the driver to react.
- Thinking distance = initial speed x reaction time

Question 10

Definition of stopping distance

Answer 10

The sun of thinking distance and braking distance for a driven vehicle

Question 11

How is speed related to thinking distance?

Answer 11

Speed is directly proportional to thinking distance
v~x

Question 12

How are braking distance and the initial speed of the car related?

Answer 12

-Braking distance is proportional to initial speed of the car squared
x~u^2

Question 13

Definition of Archimedes’ Principle

Answer 13

The upthrust acting on an object (fully or partially) submerged in a fluid is equal to the weight of fluid it displaces

Question 14

Definition of Centre of Gravity

Answer 14

The single point through which the object’s weight can be said to act

Question 15

Definition of centre of mass

Answer 15

The single point through which all the mass of an object can be said to act

Question 16

Definition of a couple

Answer 16

Two equal and opposite parallel forces that act on an object through different lines of action

Question 17

Definition of density

Answer 17

The mass per unit volume of a material. Density = mass/volume

Question 18

Definition of Drag

Answer 18

Drag is the frictional force that an object experiences when moving through a fluid

Question 19

Definition of equilibrium

Answer 19

For an object to be in equilibrium, both the resultant force and resultant moment acting on the object must be equal to zero

Question 20

Newton’s First Law

Answer 20

An object will remain at rest or constant velocity unless acted on by a resultant force

Question 21

Definition of work done

Answer 21

Force multiplied by distance moved in the direction of the force
W=Fx

Question 22

Definition of Power

Answer 22

The rate at which work is done

Question 23

Definition of a watt

Answer 23

1 watt is 1 joule per second

Question 24

Efficiency equations (write both)

Answer 24

Efficiency=(Useful energy output/total energy input )x100
Efficiency=(Useful power output/total power input)x100

Question 25

Definition of average speed

Answer 25

Average speed = total distance travelled/ time

Question 26

Newton’s Second Law

Answer 26

Resultant force is directly proportional to the rate of change of momentum

Question 27

Newton’s Third Law

Answer 27

When one body exerts a force on another, the other body exerts an equal and opposite force on the first body

Question 28

The principle conservation of momentum

Answer 28

For a closed system, the total momentum is constant (total momentum before = total momentum after)

Question 29

Definition of linear momentum

Answer 29

Linear momentum= mass x velocity (p=mv)

Question 30

Definition of a Newton

Answer 30

1 Newton is the force required to cause a mass of 1kg to have an acceleration of 1ms^-2 in the direction of the force

Question 31

Definition of Impulse

Answer 31

Impulse = Force x time for which the force acts

Question 32

Area under a force -time graph

Answer 32

=Impulse =Change in Momentum

Question 33

Definition of Impulse

Answer 33

Change in momentum
m(v-u)

Question 34

Definition of terminal velocity

Answer 34

The maximum velocity of an object that occurs when the resistive and driving forces acting as on the object are equal to each other

Question 35

Definition of a moment

Answer 35

Moment of a force = force x perpendicular distance from pivot

Question 36

Definition of torque

Answer 36

Torque of a couple = one of the forces x perpendicular distance between the forces