Forces

Question 1

What is a scalar?

Answer 1

A quantity with magnitude but no direction.

Question 2

What is a vector?

Answer 2

A quantity with magnitude and direction.

Question 3

What is a contact force?

Answer 3

Two objects touch each other to interact.

Question 4

What is Newton’s third law of motion?

Answer 4

When two objects interact with each other, they exert equal and opposite forces.

Question 5

What is Newton’s first law of motion?

Answer 5

If the forces acting on an object are balanced, the resultant force on the object is zero.

Question 6

What is a moment?

Answer 6

The turning effect of a force.

Question 7

How do you resolve a force?

Answer 7

1. Faint axis, good scale, key.
2. Measure angle and draw line to correct length.
3. Draw horizontally and vertically to the end of the line.
4. Measure both, convert both from key.

Question 8

How do you do parallelogram forces?

Answer 8

1. Draw a line of correct length, good key.
2. Draw second force line at given angle of correct length.
3. Draw mirrored opposite lines to create the parallelogram.
4. Draw a diagonal line through the shape. This is the resolving force. Measure, convert from scale.

Question 9

What is displacement?

Answer 9

The distance travelled in a given direction.

Question 10

How do you increase the size of a moment?

Answer 10

• Increase magnitude of the force.

- Increase the perpendicular distance from the line of the force to the pivot.

Question 11

What does a lever act as?

Answer 11

A force multiplier.

Question 12

What does a low gear give? Which gear turns which?

Answer 12

A low speed with a high turning effect. A small gear turns a large gear.

Question 13

What does a high gear give? Which gear turns which?

Answer 13

A high speed with a low turning effect. A large gear turns a small gear.

Question 14

What does a small gear turning a large gear do?

Answer 14

It gives low speed but a high turning effect (force).

Question 15

What does a large gear turning a small gear do?

Answer 15

It gives a low speed but a high turning effect (force).

Question 16

What does the gradient of the line on a distance-time graph represent?

Answer 16

The speed.

Question 17

What is velocity?

Answer 17

The speed of an object in a given direction.

Question 18

What is acceleration?

Answer 18

The change in velocity of an object per second.

Question 19

What does the gradient of a line on a velocity-time graph represent?

Answer 19

Acceleration.

Question 20

What happens when a resultant force acts on an object?

Answer 20

It accelerates in the direction of the resultant force.

Question 21

What does Newton’s second law of motion say?

Answer 21

Acceleration is directly proportional to the resultant force and inversely proportional to the mass.

Question 22

What is the resultant force acting on a falling object?

Answer 22

The force of gravity.

Question 23

What is terminal velocity?

Answer 23

Where the object is falling fast enough that the drag force becomes equal to the weight of the object. The velocity becomes constant.

Question 24

How is thinking distance increased?

Answer 24

The driver may be tired, drunk, on drugs or using a mobile phone.

Question 25

How is braking distance increased?

Answer 25

By poorly maintained roads, bad weather, worn tyres, worn brakes.

Question 26

Is momentum a vector or scalar?

Answer 26

A vector.

Question 27

What is the unit for momentum?

Answer 27

Kg m/s

Question 28

What is the unit for a moment?

Answer 28

Nm

Question 29

What is a closed system?

Answer 29

A system of objects that has no resultant force acting on it.

Question 30

What is the law of conservation of momentum?

Answer 30

The total momentum before the interaction of an object is equal to the total momentum after the interaction.

Question 31

What happens with an explosion with momentum?

Answer 31

One object has positive momentum and one has negative momentum.

Question 32

How is an impact force calculated?

Answer 32

Force = (mass x change in velocity) / time Change in momentum = mass x change in velocity SO Force = change in momentum / time

Question 33

What do crumple zones in cars do?

Answer 33

They increase the impact time so the force on the car is reduced.

Question 34

What do safety features in a car do?

Answer 34

- Seatbelts and airbags spread the impact force across a large area. - Airbags increase the impact time. - Seatbelts prevent flinging forward and increases impact time. - Side impact bars and crumple zones increase impact time.

Question 35

What is the relationship between extension and force applied? Who’s law is it?

Answer 35

They are directly proportional. This is Hooke’s law.

Question 36

When may a spring graph line start curving?

Answer 36

When you exceed the limit of proportionality.

Question 37

The stiffer a spring:

Answer 37

The greater it’s spring constant.

Question 38

What is the unit for pressure?

Answer 38

Pascals.

Question 39

How is pressure at a point in a liquid calculated?

Answer 39

Height of liquid x density x gfs

Question 40

The further you go down in a liquid:

Answer 40

The greater the height, so the greater the pressure.

Question 41

What is atmospheric pressure due to?

Answer 41

Collisions of air particles with surfaces.

Question 42

Why does higher altitude mean lower pressure?

Answer 42

The higher the altitude, the less weight of air there is above that altitude, so the lower the pressure. ALSO The higher the altitude, the less dense the air is as there are fewer molecules, so the lower the pressure.

Question 43

How is force experienced by an object under different pressures calculated?

Answer 43

Force = difference in pressure x the area of flat surface

Question 44

How is upthrust created in water?

Answer 44

The pressure at the bottom of an object is greater than the pressure at the top of the object. So the upward force is greater than the downward force. A resultant force is created.

Question 45

What is upthrust equal to?

Answer 45

The weight of fluid displaced.

Question 46

When does an object float?

Answer 46

When it’s weight is equal to the upthrust

Question 47

How does flotation vary with density?

Answer 47

An object that is less dense than the liquid will float. An object that is more dense than the liquid will sink.