U6 2023 - Mechanics and Materials Revision for Mock

Which row in the table is not a reasonable estimate of the physical quantity described?

• A

• B

• C

• D

Which of the following is a vector quantity?

• efficiency

• kinetic energy

• power

• weight

The wind exerts a force of 225 N on a windsurfer. The windsurfer moves a distance of 450 m at an angle of 40° to the wind, as shown.

Which of the following expressions gives the work done, in joules, on the windsurfer?

• 225 × 450

• 225 × 450 × cos 40°

• 225 × 450 × sin 40°

• 225 × 450 × tan 40°

Answer explanation

B is the correct answer.

A is wrong because the force is not acting in the direction of motion.

D is wrong because tan 40° does not give parallel component of force.

C is wrong because sin 40° does not give parallel component of force.

A student applies a force to a copper wire.

Which row of the table shows the length and diameter of wire that would produce the greatest extension?

• A

• B

• C

• D

Answer explanation

C is the correct answer.

A is wrong because shorter wire gives less extension.

B is wrong because shorter and thicker wire gives less extension.

D is wrong because thicker wire gives less extension.

A force‑extension graph for a spring is shown.

Which of the following is the work done, in joules, to extend the spring by 0.30 m from its original length?

• 0.75 J

• 0.38 J

• 8.33 J

• 0.12 J

Answer explanation

B is the correct answer.

A is wrong because this answer assumes the area under graph is a rectangle.

C is wrong because this answer comes from taking the gradient of the graph, which will not give you the work done.

D is wrong because work done is not the gradient−1 of the graph.

Two forces form a Newton’s third law pair.

Which of the following statements is not true?

• The forces act on the same object.

• The forces have the same magnitude.

• The forces act for the same time.

• The forces are the same type of force.

A student determined the acceleration of free fall g.

She measured the time t for a ball bearing to fall from rest through a distance s.

She repeated this for a range of values of s.

Which row of the table shows the graph that would give a gradient equivalent to g?

• A

• B

• C

• D

Answer explanation

B is the correct answer.

A is wrong because the gradient gives a quarter of the acceleration.

C is wrong because the gradient gives the wrong units

D is wrong because the gradient gives the wrong units.

Two identical springs are arranged in series. A force of 45.0 N is applied to the springs, as shown.

The springs extend a total distance of 15 mm.

Which of the following is the stiffness of each spring in N mm^-1?

• 0.17

• 1.5

• 0.67

• 6

The spring constants of four springs are determined by plotting the following graphs of force F against extension x.

Which order of the graphs shows decreasing spring constants?

• 2 → 1 → 3 → 4

• 3 → 4 → 2 → 1

• 4 → 2 → 1 → 3

• 4 → 3 → 2 → 1

A car is fitted with an airbag which will inflate if the car stops very suddenly.

Which of the following is increased if the airbag inflates because the car suddenly stops?

• change in momentum of the driver

• change in velocity of the driver

• force on the driver

• time that the driver takes to stop