Balanced and unbalanced forces

Four forces are applied at a point, as illustrated. What is the magnitude of the resultant force?

May/June 2015

A metal ball with mass $0.30\text{ kg}$ and weight $3.0\text{ N}$ is kept beneath the oil surface. It is acted on by an upward force of $0.30\text{ N}$. After the ball is released, what is its initial acceleration?

May/June 2015

The diagram illustrates arrows that represent two vector quantities. Which diagram shows the resultant $R$ formed by these two vectors?

May/June 2016

A man hauls a sledge with mass $25\,\text{kg}$ over level ground using a horizontal force of $60\,\text{N}$. A frictional force of $20\,\text{N}$ acts constantly on the sledge. What is the acceleration of the sledge?

May/June 2016

A man drags a sledge with mass $25\,\text{kg}$ along level ground by applying a horizontal force of $60\,\text{N}$. A frictional force of $20\,\text{N}$, acting constantly, opposes the motion of the sledge. What is the acceleration of the sledge?

May/June 2016

A sky-diver leaps out of a balloon that is stationary. At the start, his downward acceleration is $10\,\text{m s}^{-2}$. Fig. 1.1 indicates the directions of the sky-diver’s weight and the air resistance. The sky-diver has a mass of $60\,\text{kg}$ and a weight of $600\,\text{N}$.

May/June 2016

A skydiver leaves an aeroplane and, after a few seconds, attains terminal velocity without deploying his parachute. Why does he attain terminal velocity?

May/June 2017

A hanging basket is attached to a wall using a bracket. The basket has a weight of $80\,\text{N}$. The bracket has a weight of $20\,\text{N}$. What is the magnitude of the upward force applied by the wall to the bracket?

May/June 2017

Fig. 1.1 illustrates the directions of four forces acting on a racing car while it moves along a horizontal straight line. In Fig. 1.1, the arrows are labelled force A (upwards), force B(to the right), force C (downwards) and force D (to the left).

May/June 2017

Forces of $4.0\,\text{N}$ and $2.0\,\text{N}$ act at one point. Which scale diagram shows forces with a resultant of $4.0\,\text{N}$?

May/June 2018

A force of $1600\,\text{N}$ causes a car of mass $800\,\text{kg}$ to speed up from rest. What are the car’s acceleration and its velocity after $4.0\,\text{s}$?

May/June 2018

Which forces are acting on a skydiver as they fall at terminal velocity?

May/June 2018

Fig. 2.1 shows a man pushing a heavy box using a force $P$. A frictional force $F$ acts in the horizontal direction.

May/June 2018

Two forces $X$ and $Y$ act as illustrated. Which diagram shows the resultant force $R$ produced by $X$ and $Y$?

May/June 2019

Four gravitational forces acting between bodies in the Solar System are given below. $P$: the force on the Moon from the Earth $Q$: the force on the Earth from the Sun $R$: the force on the Earth from the Moon $S$: the force on the Moon from the Sun Which two forces form a Newton’s third law pair (action and reaction)?

May/June 2019

A hot-air balloon moves at constant velocity and stays at a constant height above the ground. The diagram shows the four forces acting on the balloon, and no others. Which statement is correct?

May/June 2019

Four of the gravitational forces acting between bodies in the Solar System are shown below. $P$ the force on the Moon due to the Earth $Q$ the force on the Earth due to the Sun $R$ the force on the Earth due to the Moon $S$ the force on the Moon due to the Sun Which two forces form a Newton’s third law pair (action and reaction)?

May/June 2019

A coin is dropped from rest and moves down through the air until it attains a steady speed. The diagram shows two forces P and Q, and together they produce a resultant force on the coin. How does force P change, and how does the resultant force change, before the coin attains steady speed?

May/June 2021

A coin is released from rest and moves downward through the air until it reaches a steady speed. The diagram shows two forces, $P$ and $Q$, acting on the coin so that there is a resultant force. Before the coin attains constant speed, what happens to force $P$ and what happens to the resultant force?

May/June 2021

The diagrams illustrate the forces acting on four identical solid blocks. Every arrow stands for a force of $20\ \text{N}$. Which blocks are in equilibrium?

May/June 2021

An aircraft is travelling at a fixed height. The combined effect of air drag and the force from the aircraft’s engines produces a force on the aircraft of 36 kN due north, as shown in Fig. 1.1. The wind exerts a force of 12 kN towards the east. Fig. 1.1 (not to scale) shows an aircraft with an arrow of 36 kN pointing north and an arrow of 12 kN pointing east. A north direction arrow is shown.

May/June 2021

The diagram illustrates the only two horizontal forces acting on a trolley, which is accelerating at $0.12\,\text{m s}^{-2}$. Calculate the mass of the trolley.

May/June 2023

Two people are pulling on ropes to shift a boat along a canal. The boat travels with constant velocity. The vector diagram showing the tension in the ropes is displayed. Which vector represents the drag force acting on the boat?

May/June 2024

A car moves along a road. The force exerted on the car by the engine is $800\,\text{N}$. The car’s motion depends on the magnitude of the total resistive force $R$. Which row indicates the car’s motion for the stated value of $R$?

May/June 2024

Which statement explains why a heavy coin, as it drops a short distance towards the ground, does not attain terminal velocity?

May/June 2025

Which object experiences the greatest resultant force?

Oct/Nov 2015

An apple with mass $0.15\,\text{kg}$ and weight $1.5\,\text{N}$ is dropping from a tree. At one stage of its fall, the air resistance acting on the apple is $0.60\,\text{N}$ upwards. What is the acceleration of the apple at this stage?

Oct/Nov 2015

The gravitational forces between objects in the Solar System are listed below. $P$: the force exerted on the Moon by the Earth $Q$: the force exerted on the Earth by the Sun $R$: the force exerted on the Earth by the Moon $S$: the force exerted on the Moon by the Sun Which two forces form a Newton’s third law pair (action and reaction)?

Oct/Nov 2015

Force is a vector quantity, whereas mass is a scalar quantity.

Oct/Nov 2015

Aeroplanes travel at great heights, where the temperature is far below $0^\circ\text{C}$. Ice that builds up on an aeroplane may drop to the ground and hit the surface. Fig. 9.1 shows a block of ice dropping from an aeroplane as it nears an airport. The mass of the falling block of ice is 1.2 kg and the gravitational field strength $g$ is $10\,\text{N kg}^{-1}$.

Oct/Nov 2015

Two forces with magnitudes $3.0\ \text{N}$ and $4.0\ \text{N}$ act mutually perpendicular to one another. Which diagram represents the resultant $R$ of these forces?

Oct/Nov 2016

Two forces, X and Y, act on an object to give a resultant force. The scale diagram shows the magnitudes and directions of forces X and Y. Force Z balances the resultant force from X and Y and keeps the object at rest. Which arrow shows force Z?

Oct/Nov 2016

A skydiver drops from rest through the air and attains terminal velocity. What acceleration does the skydiver have while falling?

Oct/Nov 2016

A $20\,\text{N}$ force pushes an object of mass $5.0\,\text{kg}$ forwards. Another force also acts on the object. The object has a forward acceleration of $3.0\,\text{m s}^{-2}$. What are the magnitude and direction of the other force?

Oct/Nov 2016

A skydiver is descending at terminal velocity. He then deploys his parachute. Which row shows the direction of the resultant force acting on the skydiver and the direction of the skydiver’s acceleration immediately after the parachute deploys?

Oct/Nov 2017

A skydiver in free fall leaps from an aircraft. While he is falling, an upward force and a downward force act on his body, producing a resultant force. Before terminal velocity is reached, how do the magnitudes of the forces change?

Oct/Nov 2017

Seen from above, two small tugboats are towing a large ship in a harbour. Fig. 1.1 gives the directions of the forces acting on the ship. Fig. 1.1 (not to scale) shows a ship being towed by two tugboats. Each tugboat applies a force of 49 kN to the ship. The forces are placed symmetrically at angles of 20^{\circ} above and 20^{\circ} below the centre line of the ship.

Oct/Nov 2017

An engine is towing a truck along a level track at constant speed. The connection between the engine and the truck fails. The driving force acting on the engine stays constant. What effect does this have on the engine and on the truck?

Oct/Nov 2018

An apple drops from a tree. Which row shows the forces acting on the apple and the way the apple moves as it falls?

Oct/Nov 2018

An engine is towing a truck along a level track at constant speed. The connection between the engine and the truck fails. The driving force on the engine stays constant. What effect does this have on the engine and on the truck?

Oct/Nov 2018

Which car has a resultant force acting on it?

Oct/Nov 2018

What is the magnitude of the resultant of the two forces shown in the diagram?

Oct/Nov 2019

A car is speeding up on a straight, level road. The diagram shows the forces acting on the car. Which forces are balanced?

Oct/Nov 2019

What is the magnitude of the resultant force produced by the two forces in the diagram?

Oct/Nov 2019

A heavy nail is secured tightly in a wall. A string pulls it at $40^{\circ}$ to the vertical, and the nail remains at rest. Three forces act on the nail: its weight $W$, the tension $T$ in the string, the force $R$ applied by the wall. Which diagram, drawn to scale, shows the three forces?

Oct/Nov 2020

A car with a mass of $800\,\text{kg}$ is accelerating forwards at $2.5\,\text{m s}^{-2}$. A frictional force of $1200\,\text{N}$ acts against the car's motion. What is the driving force produced by the engine of the car?

Oct/Nov 2020

A parachutist who is descending at a constant speed opens her parachute. Which row is correct for the direction of the resultant force and for the direction of the acceleration of the parachutist immediately after her parachute opens?

Oct/Nov 2020

A heavy nail is securely fixed into a wall. A string pulls on it at $40^\circ$ to the vertical. The nail remains stationary. Three forces act on the nail: - its weight $W$, - the tension $T$ in the string, - the force $R$ exerted by the wall. Which diagram, drawn to scale, shows the three forces?

Oct/Nov 2020

A car with mass $800\ \text{kg}$ has a forward acceleration of $2.5\ \text{m s}^{-2}$. A frictional force of $1200\ \text{N}$ acts opposite the car's motion. What is the driving force from the car's engine?

Oct/Nov 2020

Two forces, $X$ and $Y$, act on an object $O$. The arrows show the size and direction of the forces. Which arrow indicates the direction of the resultant force?

Oct/Nov 2021

Object X is resting on an electronic balance. Object Y is positioned above object X, as illustrated. The balance reading rises when Y is brought nearer to X. Why does this occur?

Oct/Nov 2021

A solid object is submerged in water and is suspended by an elastic thread. Three forces act on the object: its weight $W$, the tension in the thread $T$, and an upward force $F$ exerted by the water. The force $F$ is directed upwards. Which equation is correct when the object is at rest?

Oct/Nov 2021

Fig. 2.1 depicts a man with mass $80\,\text{kg}$ standing inside a lift (elevator). The gravitational field strength $g$ is $10\,\text{N kg}^{-1}$.

Oct/Nov 2021

Force is classed as a vector quantity.

Oct/Nov 2021

Three forces act on a block, as shown in the diagram. The resultant force is $6\,\text{N}$ to the right. Which extra force would give a resultant force of $3\,\text{N}$ to the left?

Oct/Nov 2022

A car with mass $1000\,\text{kg}$ is moving downhill on a very steep slope. Its brakes fail, so the driver uses a horizontal safety road filled with sand to bring the car to a halt. The car reaches the sand at a speed of $10\,\text{m s}^{-1}$ and is acted on by a constant stopping force of $2500\,\text{N}$. How far does the car move through the sand before it stops?

Oct/Nov 2022

The diagram illustrates three forces acting on a block. The resultant force is $6\,\text{N}$ to the right. Which extra force would give a resultant force of $3\,\text{N}$ to the left?

Oct/Nov 2022

A car with mass $1000\,\text{kg}$ is moving downhill on a very steep slope. When the brakes do not work, the driver uses a horizontal sand trap to bring the car to a stop. The car enters the sand at $10\,\text{m s}^{-1}$ and is acted on by a constant force of $2500\,\text{N}$ that slows it down. What distance does the car cover in the sand before it comes to rest?

Oct/Nov 2022

A wooden block rests on a table. Several external forces act on the block, yet it does not move. A student proposes three requirements for the block to stay at rest. Which of these requirements are needed for the block to stay stationary?

Oct/Nov 2022

A wooden block is pushed along a table at a steady speed. Which statement is correct?

Oct/Nov 2023

A small submarine with mass $1000\,\text{kg}$ descends through water at a steady speed of $2.0\,\text{m s}^{-1}$. What resultant force acts on the submarine while it is sinking?

Oct/Nov 2023

A force equal to the weight $W$ of the bob acts horizontally on the bob of a simple pendulum. Which diagram shows the angle between the pendulum thread and the vertical?

Oct/Nov 2024

A lorry moves on a straight, level road. The lorry has a constant driving force of $80\,\text{kN}$, while the total resistive force is $20\,\text{kN}$. Which row states how the lorry is moving and gives the resultant force on it?

Oct/Nov 2024

An object drops straight down through the air. Which diagram shows the forces acting on the object?

Oct/Nov 2024

A parachutist descends towards the ground at constant speed with a fully open parachute. Which statement is correct?

Oct/Nov 2025

An object is stationary on a table. In the free-body diagrams, the arrow lengths show the magnitude and direction of the forces acting on the object. Which diagram represents the free-body diagram for the object?

Oct/Nov 2025

Which list includes only quantities that a force can alter?

Oct/Nov 2025

A resultant force acts on an object, making it travel in a straight line. The graph illustrates how the resultant force changes with time. Which graph shows the object’s speed-time graph?

Oct/Nov 2025