Forces & elasticity

Bending or stretching objects can cause distortions.

Which of these small distortions can be described as inelastic ?

Figure 12 shows what happens when weights are added to the end of a wooden strip.

(Source: https://www.schoolphysics.co.uk/age16-19/Mechanics/Simple%20harmonic%20 motion/text/Vibrating_cantilever/index.html)

The end of the strip of wood moves down by a distance, d, as shown in Figure 12.

Describe how a student could investigate how the distance, d, depends on the weight added to the wooden strip.

A student conducts a second experiment with the same equipment where they decide to keep the size of the weight constant.

State another variable, other than the weights added, that would affect the distance, d.

Figure 13 shows a spring stretched by some weights.

The extension of the spring is 6.2 cm when a weight of 2 N is added.

Calculate the spring constant, k, of the spring.

Use the equation

spring constant, k =_........ N / m

Work is done when a spring is stretched.

A different spring has a spring constant of 25 N / m.

The spring is stretched by 0.06 m.

Calculate the energy transferred by stretching the spring.

Use the equation

energy transferred =_........

A student measures the length of a spring when it is horizontal and when it is vertical, as shown in Figures 15a and 15b.

The length, Y, of the vertical spring in Figure 15b is greater than the length, X, of the spring in Figure 15a.

Give a reason why the length of the spring in Figure 15b is greater than the length of the spring in Figure 15a.

The student adds some weights to the end of the spring, as shown in Figure 16b.

(Source: https://www.shalom-education.com/courses/ks3-physics/lessons/motion-and-forces/topic/deformation-and-hookes-law/)

The extension of the spring due to these added weights is equal to

The extension of the spring in Figure 16b is now determined for different weights added to the spring up to a maximum of 6 N.

Figure 17 shows a graph of the results.

The increase in potential energy stored in the spring is equal to the area under the graph in Figure 17.

Calculate the increase in potential energy stored in the spring when the spring is extended from 0 cm to 8 cm.

Give your answer in joules (J).

Calculate the spring constant of the spring using data from the graph in Figure 17.

State the unit.

spring constant =_........ unit_........

The box in Figure 18 represents a weight added to the end of the spring.

Figure 18

Draw two vectors on Figure 18 to complete a free body force diagram of a 5 N weight in equilibrium.

Figure 19 shows two forces, P and Q, acting at point X.

Complete the diagram in Figure 19 to show the size and direction of the resultant force, R, on point X.

Figure 16 shows part of the inside of a pen.

The pen contains a spring that can be compressed.

The spring constant of the spring is 260 N/m.

Calculate the force needed to compress the spring by the amount shown in Figure 16.

Give your answer to an appropriate number of significant figures.

A student removes the spring from the pen and investigates the compression of the spring.

Figure 17 shows the equipment and the procedure that the student uses.

ruler fixed in place above the electronic balance

The student presses down on the spring to change its length.

The electronic balance measures the force applied to the spring.

Describe how the student can determine the change in length of the spring. You may add to Figure 17 to help your answer.

The student finds it difficult to make an accurate measurement of the change in length of the spring using the equipment as shown.

Describe one way that the student could improve the procedure.

Figure 18 shows a different spring hanging from a hook fixed to the ceiling.

A block hangs from the other end of the spring.

The weight of the spring is 1 N. The weight of the block is 5 N.

The force exerted on the top of the spring by the hook is

Figure 19 shows two forces, P and Q, acting at point X.

Complete the diagram in Figure 19 to show the size and direction of the resultant force, R, on point X.

Figure 10 shows a toy used to launch a ball.

One end of the spring is fixed to the handle.

The other end of the spring is fixed to the support.

A child pulls the handle, stretching the spring.

Figure 11 shows the toy with the spring stretched.

Which of these shows the forces acting on the handle when the child keeps the spring stretched?

Ignore the force due to gravity.

In Figure 11, the extension of the spring is 0.070 m.

The spring constant (k) is 20 N/m.

Calculate the force used to extend the spring.

Use the equation

The child pulls the handle until the pad is against the support as shown in Figure 12.

The extension of the spring is 0.09 m.

The spring constant (k) is 20 N/m.

Calculate the work done in extending the spring by 0.09 m.

Use the equation

work done = ½ k(extension)²

The child lets go of the handle.

The ball starts to move.

The spring returns to its original length.

Describe the energy transfer that takes place when the ball starts to move.

The child can only stretch the spring until the pad is pressing against the support.

Explain how the design of the toy prevents the spring from becoming damaged.

Figure 14 shows a spring standing on a table.

Figure 14a
Figure 14b
Figure 14c

Weights are added to the spring as shown in Figures 14b and 14c.

Estimate the original length of the spring as shown in Figure 14a.

Describe how the reduction in the length of the spring when weights are added can be determined.

State two ways that the experimental procedure could be improved.

Give one reason why the reduction in length eventually reaches a limit as more weights are added.

A different spring is extended.

A force of 0.50 N gives an extension of 13 mm.

Calculate the spring constant k in N/m.

Another spring is extended.

The work done to extend the spring is 0.14 J.

The spring constant of the spring is 175 N/m.

Calculate the extension of the spring.

Use an equation selected from the list of equations at the end of this paper.

Figure 9 shows a 10 N weight hanging from a spring.

Figure 9

One of the forces acting to stretch the spring is shown in Figure 9.

Complete Figure 9 by adding an arrow to show the other force acting to stretch the spring.

A weight of 4.0 N is used to extend a spring. The extension of the spring is 0.06 m.

Calculate the spring constant, k, of the spring.

Use the equation

F = k × x

State what measurements should be made to determine the extension of the spring produced by the 4.0 N weight.

Another spring has a spring constant of 250 N/m.

Calculate the work done in stretching the spring by 0.30 m.

State the unit.

Use the equation

Figure 14 shows an athlete using a fitness device.

The athlete stretches the spring in the device by pulling the handles apart.

The spring constant of the spring is 140 N/m.

The athlete does 45 J of work to extend the spring.

The athlete takes 0.6 s to expand the spring.

Calculate the useful power output of the athlete when stretching the spring.

Calculate the extension of the spring.

Use an equation selected from the list of equations at the end of this paper.

A student investigates the stretching of a long piece of rubber.

Figure 15 shows the apparatus to be used.

Figure 15

The student puts just enough weight on the weight hanger to make the piece of rubber just tight.

The student wants to plot a graph to show how the extension of the piece of rubber varies with the force used to stretch it.

The student adds a known weight to the weight hanger.

Describe how the student could measure the extension of the rubber when he adds another weight to the weight hanger.

The student obtains a series of values of force and extension while loading the piece of rubber and then unloading it.

Figure 16 shows the graph of the student’s values.

Explain how the shape of this graph shows that the distortion of the piece of rubber being stretched is different from the distortion of a spring being stretched.

The area between the curve and the extension axis of a force/extension graph corresponds to work done or energy transferred.

Suggest what the shaded area of the graph in Figure 16 represents.

A student has a bar magnet, a piece of iron the same size as the magnet, and some paper clips.

Describe how the student could use these items to demonstrate temporary induced magnetism.

A student sets up the apparatus shown in Figure 9.

When the current in the solenoid is switched on, the solenoid attracts the iron nail.

Describe how the student could use this apparatus to investigate how the size of the current in the solenoid affects the force of attraction between the solenoid and the iron nail.

The spring constant of a different spring is 24 N/m.

The spring is extended from its unstretched length by 12 cm.

Calculate the energy transferred in extending the spring by 12 cm.

Use an equation selected from the list of equations at the end of this paper.