Newton's laws of motion

A student is investigating how force affects acceleration. They set up this apparatus.

Explain how they should use this apparatus to find acceleration.

Include any extra equipment they need.

Two forces act to reduce the acceleration of the car.

One of these forces is air resistance.

Name the other force.

Suggest how the teacher can reduce the effect of this other force.

The table shows the student’s results.

Suggest two changes the student could make to improve the validity of their results.

Predict the acceleration if a force of 1.2 N was applied to the car.

Use data from the table.

Acceleration =........ m / s²

Mass is an example of a quantity which has a magnitude, but no direction.

What scientific term is used for this type of quantity?

An object of mass 2.0 kg accelerates. The force acting on the object is 5.0 N.

Calculate the acceleration of the object.

Use the equation: force = mass × acceleration

0.4 m / s² A

2.5 m / s² B

3.0 m / s² C

10.0 m / s² D

The diagram shows some forces acting on a moving object.

Which statement describes the motion of the object?

A The object accelerates towards E.

B The object accelerates towards W.

C The object changes direction.

D The object moves at constant velocity.

14* A crane lifts a block straight upwards. Fig. 14.1 shows the forces acting on the block. The size of these forces may change during its journey.

Fig. 14.1

Fig. 14.2 shows the velocity-time graph for the block during a part of its journey.

Fig. 14.2

Use Fig. 14.1 and Fig. 14.2 to:

• Describe how the velocity of the block changes from point A to point E.

• Describe how the resultant force on the block changes from point A to point E.

A skydiver jumps from an airplane and reaches terminal velocity before the parachute opens.

Which statement describes what is happening when they reach terminal velocity?

A Air resistance equals the weight of skydiver.

B Air resistance has no effect on the skydiver.

C Air resistance is greater than the weight of skydiver.

D Air resistance is less than the weight of skydiver.

12* A cable is used to lift a block vertically upwards. Fig. 12.1 shows the forces acting on the block.

Fig. 12.1

The size of the resultant force on the block changes as the block is lifted. Fig. 12.2 shows the velocity-time graph for the block during the time it is being lifted.

Fig. 12.2

Describe how the motion of the block and resultant force on the block change as the block moves from point A to point G.

Use Fig. 12.1 and Fig. 12.2

The diagram shows some forces acting on a toy car.

Which row of the table describes the motion of the toy car?

Fig. 12.1 shows a picture of a ball on a field. The ball is not moving.

Fig. 12.2 shows part of a free-body force diagram for the ball.

The force is drawn to scale. 1 cm = 1 N.

Complete the free-body force diagram by adding in the missing force.

Which word describes this missing force?

Contact Electrostatic Gravity Magnetic

A person kicks the ball.

Complete the sentences explaining what happens to the ball.

Choose words from the list.

You may use each word once, more than once or not at all.

balanced

forces

gravity

masses

speed

unbalanced

The........ on the ball are........

Therefore the........ of the ball changes.

The mass of the ball is 0.4 kg.

How much force is needed to accelerate the ball at 400 m / s²?

Use the equation: force = mass × acceleration

Fig. 12.3 shows the person placing the ball so it touches a wall.

He now kicks the ball directly at the wall.

The ball changes shape. Explain why.

This is a picture of a ball on a field.

Draw a free-body force diagram for the ball.

The ball is stationary on the field. Explain why using Newton’s laws.

Student A kicks the ball with their toes.

This hurts the student’s toes. Explain why using Newton’s laws.

Student A kicks the ball.

Their boot is in contact with the ball for 0.05 s.

The velocity of the ball increases by 25 m / s.

Calculate the acceleration of the ball.

Use the equation: acceleration = change in velocity / time

Acceleration =........ m / s²

Student B kicks the ball with a force of 216 N.

The mass of the ball is 0.45 kg.

Calculate the acceleration of the ball.

Use the equation: force = mass × acceleration

Acceleration =........ m / s²

A student hangs a mass from the end of a spring as shown in Fig. 13.1.

The spring in Fig. 13.1 extends by 0.06 m. The spring constant is 25 N / m.

Calculate the force on the spring.

Use the equation: force = extension spring constant

Label the forces on the diagram in Fig. 13.2.

The loop at the end of the spring breaks and the mass falls.

Explain why the mass falls and describe its motion as it falls.

The mass is placed on a bench, as shown in Fig. 13.3.

This is a diagram showing the force of the bench on the mass.

Newton’s third law is about how forces come in pairs.

Complete the table to describe the other force in this pair.

A student measures the acceleration of a trolley on a horizontal surface.

Fig. 15.1 is a diagram of her experiment.

The weight of the masses accelerates the trolley.

Define the term weight.

Show that the weight of a 100 g mass is 1 N.

Friction can change the results of this experiment.

Suggest one way friction can be reduced.

The tall parts of the card on the trolley (U and V) pass through the light gate, as shown in Fig. 15.2.

The velocity of U is 0.5 m / s.

The velocity of V is 1.0 m / s.

Calculate the acceleration of the trolley.

Use the equation: (final velocity)² – (initial velocity)² = 2 acceleration distance

Acceleration =........ m / s²

When the trolley reaches the edge of the surface, it is moving at 1.2 m / s.

The mass of the trolley is 1.0 kg.

Calculate the kinetic energy of the trolley.

The student repeats the experiment with different masses.

This is a graph showing her results.

The student says, ‘The graph shows that the acceleration of the trolley is directly proportional to the force.’

Is the student correct?

Explain your answer.

Which statement describes Newton’s third law?

A Action and reaction are equal, opposite and act on the same object.

B Action and reaction are equal, opposite and act on separate objects.

C The rate of change of momentum is equal and opposite to resultant force.

D The rate of change of momentum is proportional to resultant force.

Student A does an experiment to find out if force is related to acceleration.

Fig. 15.1 is a diagram of her experiment.

She hangs a 400 g mass over the pulley.

How can she work out the accelerating force on the trolley?

Use an equation to help explain your answer.

The tall parts of the card on the trolley labelled X and Y pass through the light gate, as shown in Fig. 15.2.

The light gate can measure:

• the time it takes for Y to go through

• the time it takes for X to go through

• the time between Y and X going through.

How can student A use the light gate and card to measure the acceleration of the trolley?

Use an equation to help explain your answer.

Describe one way this experiment could be improved.

* Student A records some measurements. She plots the data points and draws a line of best fit on the graph in Fig. 15.3.

Describe and explain what the results in Fig. 15.3 show. Comment on the validity of student A ’s results shown on the graph in Fig. 15.3.

You are not expected to include a calculation.

Student B does the same experiment.

Fig. 15.4 is a graph of her results.

Calculate the gradient of the graph in Fig. 15.4.

Gradient =........ per kg

Student B ’s graph in Fig. 15.4 can be described by an equation.

Write this equation in the form: y = mx + c

Use your answer to 15(e)(i) and student B ’s graph in Fig. 15.4 to help you.

During launch, a rocket accelerates when the upwards force is greater than the downwards force.

Name the upwards and downwards forces on the rocket during launch.

At launch, the upwards force is 10 000 N and the downwards force is 8 000 N.

Write down the size of the resultant force in Newtons.

The rocket has a mass of 800 kg.

Calculate its acceleration.

Use the equation: Force = Mass × Acceleration

How can mass be calculated?

A Acceleration divided by force

B Force divided by acceleration

C Gravity divided by weight

D Weight divided by force