Forces & elasticity

Figure 14 shows how the extension of three different springs varies with the force applied to each spring.

Describe the relationship between force and extension for spring A.

Which spring in Figure 14 has the greatest spring constant?

Give a reason for your answer.

Tick () one box.

Spring A Spring B Spring C

Reason

Figure 15 shows a baby in a ‘baby-bouncer’.

The baby sits in a harness which is held by a spring.

When the baby jumps, the baby bounces up and down.

The spring of the baby-bouncer is extended by 0.60 m.

The elastic potential energy stored by the spring is 75.6 J.

Calculate the spring constant of the spring.

Use the Physics Equations Sheet.

Choose the unit from the box.

The spring does not extend past the limit of proportionality when the baby is in the baby-bouncer.

How does the work done to stretch the spring compare with the elastic potential energy stored in the spring?

Tick () one box.

Work done is less than elastic potential energy stored.

Work done is equal to elastic potential energy stored.

Work done is greater than elastic potential energy stored.

Figure 1 shows how the extension of three different springs varies with the force applied to each spring.

Describe the relationship between force and extension for spring A.

Which spring in Figure 1 has the greatest spring constant?

Give a reason for your answer.

Tick () one box.

Spring A Spring B Spring C

Reason

Figure 2 shows a baby in a ‘baby-bouncer’.

The baby sits in a harness which is held by a spring.

When the baby jumps, the baby bounces up and down.

The spring of the baby-bouncer is extended by 0.60 m.

The elastic potential energy stored by the spring is 75.6 J.

Calculate the spring constant of the spring.

Use the Physics Equations Sheet.

Choose the unit from the box.

The spring does not extend past the limit of proportionality when the baby is in the baby-bouncer.

How does the work done to stretch the spring compare with the elastic potential energy stored in the spring?

Tick () one box.

Work done is less than elastic potential energy stored.

Work done is equal to elastic potential energy stored.

Work done is greater than elastic potential energy stored.

Figure 8 shows a student about to launch a toy aeroplane horizontally.

The student pulled on the aeroplane to stretch the spring.

The student then released the aeroplane.

After the aeroplane was released, the aeroplane accelerated until it passed the student’s hand.

Describe how the energy stores of the aeroplane and spring changed as the aeroplane accelerated.

The spring exerted a force on the aeroplane to make the aeroplane accelerate.

As the aeroplane accelerated, it moved through a distance of 40 cm.

The work done by the spring on the aeroplane was 3.0 J.

Calculate the mean force exerted by the spring on the aeroplane.

Use the Physics Equations Sheet.

The student launched the aeroplane at different angles to the horizontal.

The student then measured the horizontal distance travelled by the aeroplane.

Figure 9 shows the launch angle of the aeroplane.

After being launched, the aeroplane flew through the air and landed on the ground.

Figure 10 shows how the horizontal distance travelled varies with the launch angle.

The extension of the spring was the same in each test.

Describe how the horizontal distance travelled varies with the launch angle.

Explain how increasing the extension of the spring would affect the horizontal distance travelled by the aeroplane.

Figure 7 shows two people wearing inflatable bodysuits.

The bodysuits are made of soft plastic and are inflated with air.

The bodysuits reduce the chance of injury in a collision.

Explain how wearing a bodysuit reduces the chance of injury in a collision.

Figure 8 shows person A about to collide with person B.

The arrows show the direction in which each person is moving.

The velocity of person A is + 2.0 m/s.

The two people collide and stop.

Calculate the velocity of person B before the collision.

Use the Physics Equations Sheet.

Figure 9 shows a person in an inflatable sphere rolling down a hill.

The total mass of the person and sphere is 80 kg.

The sphere moves through a vertical height of 6.4 m.

gravitational field strength = 9.8 N/kg

Calculate the maximum possible speed of the sphere at the bottom of the hill.

Use the Physics Equations Sheet.

The actual speed of the sphere at the bottom of the hill is much less than the maximum possible speed.

Explain why.

Figure 1 shows a floating hot air balloon attached to the ground by a rope.

The hot air balloon is stationary.

The wind is exerting a force on the hot air balloon in Figure 1.

Which arrow shows the direction of the force of the wind in Figure 1 ?

Tick (✓) one box.

Which force causes the hot air balloon to float?

Tick (✓) one box.

Air resistance

Gravity

Upthrust

The hot air balloon in Figure 1 is stationary.

What is the resultant force on the balloon?

Tick (✓) one box.

The resultant force is the tension in the rope.

The resultant force is the weight.

The resultant force is zero.

The mass of the hot air balloon is 350 kg.

Calculate the weight of the hot air balloon.

gravitational field strength = 9.8 N/kg

Use the equation:

_ weight = mass × gravitational field strength

The hot air balloon exerts a force of 200 N on the rope.

The force causes the rope to stretch by 1.60 m.

The rope behaves like a spring.

Calculate the spring constant of the rope.

Use the equation:

Choose the unit from the box.

A student investigated how the extension of a spring varied with the force applied to the spring.

Figure 13 shows the equipment used.

This is the method used.

1. Measure the length of the unstretched spring.

2. Hang the spring from the clamp stand.

3. Hang a mass from the spring.

4. Calculate the weight of the mass.

5. Measure the new length of the spring.

6. Calculate the extension of the spring.

7. Repeat steps 3 to 6 for additional masses.

A spring can be elastically or inelastically deformed.

What does ‘elastically deformed’ mean?

Figure 14 shows the results.

The student concluded:

‘The extension of the spring is directly proportional to the weight up to a point called the limit of proportionality.’

What was the extension of the spring when the spring reached its limit of proportionality?

Determine the spring constant of the spring used by the student.

Use the Physics Equations Sheet.

The mass on the spring is stationarity after the spring has extended.

The force that the mass exerts on the spring is represented by the vector diagram in Figure 15.

Draw an arrow on Figure 15 to show the magnitude and direction of the tension in the spring.

Figure 4 shows a student launching a toy aeroplane.

The student pulls on the aeroplane to stretch the spring and then lets go of the aeroplane.

Give one factor that would affect how high the aeroplane goes.

The extension of the spring is 0.20 m.

Calculate the elastic potential energy stored by the spring.

spring constant = 27 N/m

Use the equation:

elastic potential energy = 0.5 × spring constant × (extension)²

A student investigated how the extension of the spring varied as the force on the spring was increased.

Figure 5 shows the results.

What is a correct conclusion about the relationship between force and extension from 0 to 9 N?

Tick (✓) one box.

Force and extension are inversely proportional.

Force and extension have a linear relationship.

Force and extension show a negative correlation.

The spring in Figure 5 was stretched inelastically.

What was the extension when the spring was at the limit of proportionality?

Tick (✓) one box.

9 cm 34 cm 40 cm

Give a reason for your answer.

Figure 6 shows what happened to the extension of the spring as the force was decreased.

Describe what happened to the spring as the force was decreased from 10 N to 0 N.

Figure 16 shows a student using a catapult to launch a small stone.

The catapult contains a spring.

What is the relationship between the extension of a spring and the force applied to the spring?

The extension of the spring is 20 cm.

The elastic potential energy stored by the spring is 1.16 J.

Calculate the spring constant of the spring.

Use the Physics Equations Sheet.

The student used the catapult to launch stone A and then stone B.

The spring had the same extension for each stone.

Stone B has a mass 4 times greater than stone A.

Explain the difference in the speed of stone A and the speed of stone B as they are launched from the catapult.

Your answer should include a calculation.

Use the Physics Equations Sheet.

Some catapults use a rubber band instead of a spring.

A student investigated how the extension of a rubber band varied with the force on the rubber band.

Figure 17 shows the results.

Explain why additional readings would allow the student to make a conclusion more easily.

Do not refer to repeat readings or calculating a mean.

Figure 12 shows the equipment a student used to investigate the effect of weight on the distance a box slides.

This is the method used.

1. Put a 1.0 N weight in the box.

2. Pull the box backwards until it reaches the start line, extending the rubber band by 10 cm.

3. Release the box.

4. When the box stops moving, measure the distance the box has slid using the metre rule.

5. Repeat steps 2 to 4 using a weight of 2.0 N and then 3.0 N.

The extension of the rubber band was a control variable in the investigation.

Suggest one other control variable in the investigation.

Table 4 shows the results when the weight inside the box was 1.0 N.

What was the uncertainty in the distance measurements when the weight inside the box was 1.0 N?

Tick (✓) one box.

±0.1 cm
±0.4 cm
±0.8 cm
±1.0 cm

The rubber band was extended by 10 cm.

The rubber band behaves like a spring with a spring constant of 36 N/m.

Calculate the elastic potential energy stored by the rubber band.

Use the Physics Equations Sheet.

What is the maximum possible value for the kinetic energy of the box?

Table 5 shows the student’s results.

Describe improvements the student could make to the method.

Use information from:

Figure 2 shows the equipment a student used to investigate the effect of weight on the distance a box slides.

This is the method used.

1. Put a 1.0 N weight in the box.

2. Pull the box backwards until it reaches the start line, extending the rubber band by 10 cm.

3. Release the box.

4. When the box stops moving, measure the distance the box has slid using the metre rule.

5. Repeat steps 2 to 4 using a weight of 2.0 N and then 3.0 N.

The extension of the rubber band was a control variable in the investigation.

Suggest one other control variable in the investigation.

Table 1 shows the results when the weight inside the box was 1.0 N.

What was the uncertainty in the distance measurements when the weight inside the box was 1.0 N?

Tick (✓) one box.

±0.1 cm
±0.4 cm
±0.8 cm
±1.0 cm

The rubber band was extended by 10 cm.

The rubber band behaves like a spring with a spring constant of 36 N/m.

Calculate the elastic potential energy stored by the rubber band.

Use the Physics Equations Sheet.

What is the maximum possible value for the kinetic energy of the box?

Table 2 shows the student’s results.

Describe improvements the student could make to the method.

Use information from:

A student investigated how the extension of a spring varied with the force acting on the spring.

Figure 14 shows the equipment the student used and a ruler scale between 10 cm and 15 cm

Describe how the student should determine the extension of the spring.

Write down the equation which links extension (e), force (F) and spring constant (k).

The extension of the spring was 0.12 m when the force was 3.0 N

Calculate the spring constant of the spring.

Spring constant = N/m

Figure 15 shows the results of the same investigation using a different spring.

The spring constant of the spring was 40 N/m

Determine the energy stored by the spring when the force was 3.6 N

Use the Physics Equations Sheet.

A student investigated how the extension of a spring varied with the force acting on the spring.

Figure 3 shows the equipment the student used and a ruler scale between 10 cm and 15 cm

Describe how the student should determine the extension of the spring.

Write down the equation which links extension (e), force (F) and spring constant (k).

The extension of the spring was 0.12 m when the force was 3.0 N

Calculate the spring constant of the spring.

Spring constant = N/m

Figure 4 shows the results of the same investigation using a different spring.

The spring constant of the spring was 40 N/m

Determine the energy stored by the spring when the force was 3.6 N

Use the Physics Equations Sheet.