Mechanics

Question 1

What are the vector quantities?

Answer 1

Displacement, velocity, acceleration, force, momentum

Question 2

How do you calculate displacement from a velocity time graph?

Answer 2

Calculate the area under the graph

Question 3

How do you calculate displacement from a velocity time graph if it is curved?

Answer 3

Use the count the squares method

Question 4

What is the definition of stopping distance?

Answer 4

Total distance travelled from when the driver first sees the reason to stop to when the vehicle stops.

Question 5

What is the equation for stopping distance?

Answer 5

Stopping distance = thinking distance + braking distance

Question 6

What is the definition of thinking distance?

Answer 6

Distance travelled between moment when you first sees a reason to stop, to the moment when you use the brake.

Question 7

What is the definition of braking distance?

Answer 7

The distance travelled from the time the brake is applied until the vehicle stops.

Question 8

What factors affect stopping distance?

Answer 8

Speed of vehicle, condition of brakes, condition of tires, condition of the road, weather conditions, alertness to the driver.

Question 9

What is the equation for thinking distance?

Answer 9

Thinking distance = speed x reaction time

Question 10

How would you calculate braking distance?

Answer 10

Use SUVAT equations

Question 11

How would you draw a scale drawing?

Answer 11

Decide on a scale for the length of vectors and use a protractor to draw angles accurately. Measure the length of the unknown vector and convert to Newtons using the scale.

Question 12

What is the definition of drag?

Answer 12

A frictional force that resists the motion of an object through a fluid.

Question 13

Define a Newton

Answer 13

The force that causes a mass of
one kilogram to have an acceleration of one metre per second squared.

Question 14

When and why is F=ma no longer valid?

Answer 14

Due to Einstein’s Theory of Special Relativity, mass increases if the object is travelling very close to the speed of light.

Question 15

Define centre of mass of an object

Answer 15

The single point that you can consider its whole weight to act through.

Question 16

Where is the centre of gravity for a regular shaped object?

Answer 16

Where its lines of symmetry meet.

Question 17

Where does the centre of mass act for a uniform object?

Answer 17

At the centre of the object.

Question 18

Define a moment

Answer 18

Moment = force x perpendicular distance to the line of action of the force from the axis or point of rotation

Question 19

Define the principle of moments

Answer 19

For a body in equilibrium, the sum of the anticlockwise moments about any point is equal to the sum of the clockwise moments about that same point.

Question 20

Define a couple

Answer 20

A pair of forces equal in size acting parallel to each other but in opposite directions.

Question 21

What features must a couple have?

Answer 21

Forces must be equal in magnitude
Forces must be parallel but opposite in direction
Forces must be separated by a distance d

Question 22

Define torque of a couple

Answer 22

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

Question 23

Define work done

Answer 23

Work done = force x displacement in the direction of the force

Question 24

Define a Joule

Answer 24

1 Joule is equal to the work done by a 1 Newton force moving an object through 1 metre.

Question 25

Define the principle of conservation of energy

Answer 25

Energy cannot be created or destroyed, it transfers between different forms.

Question 26

Define power

Answer 26

Rate of energy transfer

Question 27

Define a Watt

Answer 27

Work done of 1 Joule in 1 second

Question 28

Why is no mechanical device 100% efficient?

Answer 28

There is always a waste heat due to work done against resistive forces such as friction.

Question 29

Define pressure

Answer 29

Force per unit area

Question 30

Define Pascal

Answer 30

1 Newton per metre squared

Question 31

What do the letters represent in the equation p = ρgh?

Answer 31

p - pressure at the base of the column ρ - density of the fluid h - height of the column

Question 32

State archimedes principle

Answer 32

For an object fully or partly submerged in a fluid, there is a force of upthrust equal to the weight of the fluid displaced.

Question 33

What happens to wood released from the bottom of a tank full of water?

Answer 33

It will eventually float, as the wood speeds up the drag will increase, it may reach terminal velocity if W + D = U before the surface.

Question 34

Write an equation for the forces acting on wood when it floats

Answer 34

W = U

Question 35

Why does a mass still have some kinetic energy at max height?

Answer 35

It has a horizontal component of KE

Question 36

What does the magnitude of drag depend on?

Answer 36

Cross sectional area of the moving object Viscosity of fluid Velocity of object Roughness of surface of the object

Question 37

What is the equation for upthrust?

Answer 37

F = ρVg