P8 - Forces In Balance

Question 1

What is a vector quantity?

Answer 1

A physical quantities with size(magnitude)AND direction.

Question 2

What is a scalar quantity?

Answer 2

A physical quantity with size but no direction.

Question 3

What is displacement?

Answer 3

Distance without a change in direction.

Question 4

What is velocity?

Answer 4

Speed at a certain direction.

Question 5

What is weight?

Answer 5

How much NEWTONS you weigh on a certain planet.

Question 6

What is mass?

Answer 6

How much matter something has.

Question 7

What is a force.

Answer 7

A push or a pull that acts on an object.

Question 8

What is force measured in?

Answer 8

Newtons(N)

Question 9

List the contact forces.

Answer 9

Friction
Tension
Air resistance
Thrust

Question 10

List the non-contact forces.

Answer 10

Gravitational
Magnetic
Electrostatic
Nuclear

Question 11

What is Newtons 1st law?

Answer 11

An object at rest remains at rest, and an object in motion remains in motion at constant speed.

Question 12

What is Newtons 2nd law?

Answer 12

The acceleration of an object is directly proportional to the resultant force of the object but inversely proportional to the mass of the object.

Question 13

What is Newtons 3rd law?

Answer 13

For every action there is an equal and opposite reaction. They are equal in magnitude.

Question 14

What is friction?

Answer 14

Friction is the force exerted by a surface against an object when it moves across it.

Question 15

What is the resultant force?

Answer 15

A single force that has the same effect as all the forces acting on an object.

Question 16

What is Newton’s first law of motion?

Answer 16

If the resultant force acting on an object is zero, all the forces are said to be balanced.
- If the object is stationary, it will remain stationary .
- If the object is moving, it will continue to move at the same speed and in the same direction.

Question 17

Name 3 vector quantities.

Answer 17

Acceleration
Velocity
Force
Weight
Displacment

Question 18

Name 3 scalar quantities

Answer 18

Mass
Speed
Time
Distance
Energy
Power

Question 19

How are vector quantities represented?

Answer 19

-Vectors can be represented by an arrow
- The direction of the arrow shows the direction of the vector.
- The length of the arrow shows the magnitude.

Question 20

What is the definition of contact forces?

Answer 20

A force that occurs when objects are physically touching.

Question 21

What is the definition of non-contact forces?

Answer 21

A force that occurs when objects are physically separated.

Question 22

What does upthrust do?

Answer 22

The upward force acting on an object in a fluid, due to it experiencing a greater pressure below it than above it.

Question 23

What does air resistance do?

Answer 23

It tries to stop things moving throught the air.

Question 24

What does a reaction do?

Answer 24

It stops things going through solid objects - normal contact force.

Question 25

What does thrust do?

Answer 25

Thrust is a force that pushes objects forward.

Question 26

If the resultant force is zero what does it mean?

Answer 26

All the forces acting on the object are balanced.

Question 27

Recall unbalanced forces.

Answer 27

If the resultant force acting on an object is not zero all the forces are said to be unbalanced. The speed of the object and the direction of motion may change.

Question 28

What is terminal velocity?

Answer 28

The maximum velocity that an object can attain when it is falling through a fluid, such as air or water.

Question 29

What are moments?

Answer 29

Moments are the turning force around a fixed pivot. It can act in a clockwise or anticlockwise motion .

Question 30

What are ways to increase a moment?

Answer 30

Increasing the distance from the pivot (get a longer spanner). Increase the force applied.

Question 31

What is the equation to find a moment?

Answer 31

Force(N) x perpendicular distance(m) = moment(Nm)

Question 32

What is a lever?

Answer 32

A lever is a rigid body that is capable of lifting a heavy load with small effort. It is a force multiplier.

Question 33

What are force multipliers?

Answer 33

Force multipliers multiply the applied foce, allowing you to lift more for less work - they increase the effect of a force.

Question 34

How do you calculate gear ratio?

Answer 34

Number of teeth on the driven/number of teeth on the driver.

Question 35

How do you calculate moments in gears?

Answer 35

Moment = Force x Gear radius

Question 36

What is the gear called that turns the other gears- puts in the effort.

Answer 36

The driver

Question 37

What are the gears called that are turned by the driver?

Answer 37

The driven.

Question 38

What is the centre of mass of an object?

Answer 38

The centre of mass of an object is the point at which its mass can be thought of as being concentrated.

Question 39

Describe how to find the centre of mass of regular shaped objects.

Answer 39

You would find the centre of mass by drawing lines from one corner to the parallel corner.

Question 40

What is a plumb line used for?

Answer 40

A plumb line is used for finding the centre of mass of an irregular shaped object.

Question 41

Explain how a plumb line is used on an irregular object to find the centre of mass.

Answer 41

1. The irregular object is hanged freely, where the plumb line is attached underneath. The centre of mass is always below, in line with the thread. 2.Suspend the card attach the plumb line. Using a pencil and a ruler draw a line along the plumb line. 3.Repeat the last step from a different point. Centre of mass is where the lines cross.

Question 42

State the principle of moments.

Answer 42

The sum of all the clockwise moments about any point = The sum of all anticlockwise moments about that point

Question 43

What are the two possible scenarios for motion when the resultant force on an object is zero?

Answer 43

Stationry or a constant velocity

Question 44

How can you calculate the resultant force of two forces?

Answer 44

You can calculate resultant forces by using the parallelogram of forces.

Question 45

How do you draw a parallelogram of forces.

Answer 45

Step 1: Work out a scale Step 2: Copy out one force - The length needs to be drawn to scale. Step 3: Measure the angle Step 4: Draw the next Step 5: Set your compass to the size of one of the forces. Step 6: Place the compass point at the end of the other force and draw an arc. Step 7: Set your compass to the size of the other force. Step 8: Place the compass at the end of the other force and draw a second arc. Step 9: Draw the resultant force from the ship to the point where the two arcs cross. Step 10: Using a ruler measure the size of the resultant force. Step 11: Calculate the size of the resultant force.

Question 46

Give a detailed process of how to resolve forces in equilibrium.

Answer 46

1.First we can draw a geometric ‘scaled’ free body diagram with our weight acting straight down to ground. 2.Draw the force acting normal to the slope and the force acting along side/parallel to the slope to form parallelogram. 3.Measuring FN and FH will give use their magnitude and we can also get their angle easily.