A moment is best described as...

• a force acting parallel to a distance from a pivot.

• a force acting over a distance.

• the rotation of an object.

• a force acting at a perpendicular distance from a pivot.

Two children, A and B, are sitting on a see-saw, as shown in the figure below.

The see-saw is balanced.

Calculate the moment of child B about the pivot of the see-saw in N m. (just write the value, no units needed)

Two children, A and B, are sitting on a see-saw, as shown in the figure below.

The see-saw is balanced.

Calculate the weight of child A if they are sitting 80 cm from the pivot of the see-saw in N. (just write the value, no units needed)

A camera boom is used at a television studio to allow filming from different positions.

Figure 1 shows the arm of the boom in three different positions.

In which position will the weight of the camera cause the largest moment about the pivot?

• A

• B

• C

• They are all the same moment.

A camera boom is used at a television studio to allow filming from different positions.

Complete the sentence.

When the moment caused by the weight of the camera increases, the moment caused by the counterweight ____________________ .

• decreases

• does not change

• increases

• They are all the same moment.

The camera has a mass of 5.0 kg

gravitational field strength = 9.8 N/kg

Calculate the weight of the camera. write the unit symbol with your answer.

Figure 2 shows the 5 kg camera boom in a new position, D.

Calculate the moment about the pivot caused by the weight of the camera when the arm of the boom is in position D in Nm. (no unit needed)

Calculate the pulling force that is needed in the steel cable to keep the jib horizontal. (No unit needed)

The diagram shows an air-driven toy.

When the electric motor is switched on the fan rotates.

The fan pushes air backwards making the toy move forwards.

The toy has a mass of 0.15 kg and moves forward with a velocity of 0.08 m/s.

How is the momentum of the toy calculated?

• 0.15 + 0.08 = 0.230

• 0.15 ÷ 0.08 = 1.875

• 0.15 × 0.08 = 0.012

What are the unit of momentum?

• kg m/s

• m/s²

• kg/m/s