P3 - Making things work

Question 1

A plumb line always hangs so that it is….?

Answer 1

Vertical

Question 2

How can you make an object more stable?

Answer 2

Lower the centre of mass and give it a wide base.

Question 3

Use the terms ‘line of action of the weight’ and ‘resultant moment’ to explain why a stable concrete mixer does not fall over when it is given a small push.

Answer 3

The line of action falls inside the base and resultant moment will return the mixer to the original position.

Question 4

What is the unit for time period?

Answer 4

second

Question 5

How does using a shorter piece of rope for a swing change the time period?

Answer 5

Decreases the time period.

Question 6

Where is the centre of mass of a tyre?

Answer 6

In the centre of the tyre because this is where the axes of symmetry cross.

Question 7

What goes in the gap: A suspended object will come to rest with its centre of mass directly……the point of suspension.

Answer 7

below

Question 8

What is meant by the centre of mass of an object?

Answer 8

The point at which the mass seems to act/ point at which gravity seems to act.

Question 9

When packing a suitcase, why should you put the heaviest items at the end where the wheels are?

Answer 9

It lowers the centre of mass so the suitcase is more stable when pulled; the turning effect is less so the pull on your arms is less.

Question 10

What is the meaning of the term moment?

Answer 10

Turning force

Question 11

What does the term stable mean in physics?

Answer 11

The centre of mass remains above the base.

Question 12

Explain why using a longer steel bar would make it easier for a gardener to lever a tree stump out of the ground.

Answer 12

The force is applied further from the pivot which causes an increased moment to act on the steel bar and therefore an increased force acts on the tree stump.

Question 13

Give two ways in which you can increase the turning effect of a spanner.

Answer 13

Lengthen the spanner or apply a bigger force.

Question 14

Explain why there are large concrete blocks at the end of a crane behind the operator’s cabin.

Answer 14

The mass of the concrete blocks can be altered depending on the mass of the object lifted so that the crane remains stable and the total clockwise moment= total anticlockwise moment and the centre of mass of the crane remains above the base.

Question 15

Why can liquids be used to transmit the forces in a brake system?

Answer 15

Because they are incompressible.

Question 16

In a hydraulic brake, the pressure in the liquid is transmitted in which direction?

Answer 16

In all directions

Question 17

What unit is usually used when calculating pressure?

Answer 17

Pa (Pascal)

Question 18

If a rider applies a larger force to the brake lever, how would this increase in force affect the pressure in the brake fluid?

Answer 18

It increases

Question 19

A hydraulic jack is an example of what?

Answer 19

A force multiplier

Question 20

Explain how the wheel of the London eye can move at a steady speed and the capsules accelerate at the same time.

Answer 20

Acceleration occurs when the direction changes. As velocity has direction, acceleration, which is the rate of change in velocity, changes.

Question 21

What is the name of the resultant force that causes the capsules of the London eye to accelerate as the wheel moves at a steady speed?

Answer 21

Centripetal force