Forces & elasticity

Bending or stretching objects can cause distortions.

Which of these small distortions can be described as inelastic ?

Figure 7 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 7.

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 8 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 9a and 9b.

The length, Y, of the vertical spring in Figure 9b is greater than the length, X, of the horizontal spring in Figure 9a.

Give a reason why the length of the spring in Figure 9b is greater than the length of the the spring in Figure 9a.

The student adds some weights to the end of the spring, as shown in Figure 10b.

(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 10b is now determined for different weights added to the spring up to a maximum of 6 N.

Figure 11 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 11.

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 11.

State the unit.

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

The box in Figure 12 represents a weight added to the end of the spring.

Figure 12

Draw two vectors on Figure 12 to complete a free body force diagram of a 5 N weight in equilibrium.

Figure 13 shows two forces, P and Q, acting at point X.

Complete the diagram in Figure 13 to show the size and direction of the resultant force, R, on point X.

Figure 6 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 6.

Give your answer to an appropriate number of significant figures.

force =_........ N

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

Figure 7 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 7 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 8 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 9 shows two forces, P and Q, acting at point X.

Complete the diagram in Figure 9 to show the size and direction of the resultant force, R, on point X.

Figure 3 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 4 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 4, 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

force =_........ N

The child pulls the handle until the pad is against the support as shown in Figure 5.

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 = ½k(extension)²

work done =_........ J

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 9 shows a spring standing on a table.

Weights are added to the spring as shown in Figures 9b and 9c.

Estimate the original length of the spring as shown in Figure 9a.

original length =_........ mm

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.

spring constant k =_........ 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.

extension of spring =_........ m

Figure 4 shows a 10 N weight hanging from a spring.

Figure 4

One of the forces acting to stretch the spring is shown in Figure 4.

Complete Figure 4 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

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

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

work done in stretching the spring =_........ unit_........

Figure 7 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.

useful power output of the athlete =_........ W

Calculate the extension of the spring.

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

extension of the spring =_........ m

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

Figure 8 shows the apparatus to be used.

Figure 8

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 9 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 9 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 4.

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.

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