AQA A-level Physics: Year 2 Student Book

Page 20

12 the StReNGth OF MAteRIALS

PRACTICE QUESTIONS 1. A type of exercise device is used to provide resistive forces when a person applies compressive forces to its handles. The stiff spring inside the device compresses as shown in Figure Q1. spring

force exerted by person

ii. The person causes a compression of 0.28 m in a time of 1.5 s. Use the graph in part a to calculate the average power developed. AQA Unit 2 January 2011 Q1

compression metal tubes handles

Explain how this formula can be derived from a graph of force against extension.

L

force exerted by person

2. A cable-car system is used to transport people up a hill. Figure Q3 shows a stationary cable car suspended from a steel cable of cross-sectional area 2.5 × 10–3 m2. cable

Figure Q1

a. The force exerted by the spring over a range of compressions was measured. The results are plotted on the grid in Figure Q2.

cable car

Figure Q3

500

a. The graph in Figure Q4 is for a 10 m length of this steel cable. Use the graph to calculate the initial gradient, k, for this sample of the cable.

300 200

3.0

100

2.5

0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 Compression, L / m Figure Q2

i.

State Hooke’s law.

ii. State which two features of the graph confirm that the spring obeys Hooke’s law over the range of values tested. iii. Use the graph to calculate the spring constant, stating an appropriate unit. b. i. The formula for the energy stored by the spring is E=

1 2

Load / 105 N

Force / N

400

2.0 1.5 1.0 0.5 0.0 0.0

1.0

2.0 3.0 4.0 5.0 Extension / 10−3 m

6.0

7.0

Figure Q4

F ΔL

294

90223_P278_297.indd 294

27/05/15 3:46 PM


Turn static files into dynamic content formats.

Create a flipbook
Issuu converts static files into: digital portfolios, online yearbooks, online catalogs, digital photo albums and more. Sign up and create your flipbook.