Instructions
Read each question carefully. For the objective questions, circle the best answer. For the subjective and problem-solving questions, write your answers in the space provided. Good luck!
Part A: Objective Questions
Circle the letter of the best answer for each question.
- What is a force?
- a) The amount of matter in an object
- b) A push or a pull
- c) The speed of an object
- d) The color of an object
- Which of the following is an effect of an unbalanced force?
- a) An object remains stationary
- b) An object's shape changes
- c) An object continues moving at a constant velocity
- d) All of the above
- The force that pulls all objects towards the center of the Earth is called:
- a) Friction
- b) Magnetic Force
- c) Gravity
- d) Air Resistance
- Which of these is an example of a non-contact force?
- a) Pushing a shopping cart
- b) Kicking a football
- c) A magnet picking up a paperclip
- d) Writing with a pencil
- Friction is a force that:
- a) Speeds up motion
- b) Opposes motion
- c) Works only on objects in the air
- d) Pulls objects downwards
- When you squeeze a sponge, you are using a force to change its:
- a) Mass
- b) Color
- c) Shape
- d) Weight
- If two teams in a tug-of-war pull with the exact same force, the forces are:
- a) Unbalanced
- b) Frictional
- c) Gravitational
- d) Balanced
- The unit used to measure force is the:
- a) Meter (m)
- b) Kilogram (kg)
- c) Newton (N)
- d) Second (s)
- A cyclist pedaling faster is applying more force to:
- a) Decrease their speed
- b) Change their direction
- c) Increase their speed
- d) Stop the bicycle
- Which surface would have the MOST friction?
- a) A sheet of ice
- b) A polished wooden floor
- c) A grassy field
- d) A sheet of glass
Mark the following statements as True (T) or False (F).
- ____ A force can change the direction of a moving object.
- ____ Gravity is a type of contact force.
- ____ Balanced forces acting on an object will cause it to accelerate.
- ____ Air resistance is a type of friction.
- ____ A weaker push will make an object travel farther than a stronger push.
- ____ A magnet uses magnetic force to attract iron objects.
- ____ To stop a moving ball, you need to apply a force.
- ____ The shape of an object can never be changed by a force.
- ____ Friction is always a disadvantage.
- ____ An object at rest has no forces acting on it.
Part B: Subjective Questions
Write a short answer for each question.
- Define "unbalanced forces" and explain what happens to an object when they are applied.
- Give two examples of how friction is helpful in everyday life.
- Explain the difference between a contact force and a non-contact force. Provide one example of each.
- What are the four things a force can do to an object?
- Why does a feather fall more slowly than a stone of the same size?
- If you kick a football, it eventually stops. Name two forces that cause it to stop.
- What is gravity? Does it affect all objects?
- How can you reduce friction between two surfaces? Give one method.
- Describe what happens to a moving bicycle when the rider applies the brakes. Use the word "force" in your answer.
- A book is sitting still on a table. Are there any forces acting on it? Explain your answer.
Part C: Problem-Solving Questions
Read the scenarios and answer the questions.
- Imagine you are pushing a heavy box across a room. At first, it's very hard to get it moving, but it gets a little easier once it's already sliding. Why do you think this is?
- Two friends, Alex and Sam, are pushing a large boulder. Alex pushes with a force of 100 Newtons to the right. Sam pushes with a force of 80 Newtons to the right. Will the boulder move? If so, in which direction? What is the total force being applied in that direction?
- A paratrooper jumps from a plane. When they first jump, they fall very fast. Then, they open their parachute and their speed slows down dramatically. Explain the forces at play in both situations (before and after the parachute opens).
- You are playing with two toy cars. Car A has smooth plastic wheels. Car B has rubber wheels with deep treads. You race them both down a ramp onto a carpet. Which car do you predict will stop first, and why?
- You are trying to close a gate on a windy day. The wind is pushing the gate open while you are trying to push it closed. Describe a situation where the gate would not move at all, and a situation where you would be able to close the gate. Use the terms "balanced" and "unbalanced" forces in your answer.
Answer Key
Part A: Objective Questions
- b) A push or a pull
- b) An object's shape changes (Unbalanced forces cause a change in motion, which includes starting/stopping or changing direction, or they can change an object's shape.)
- c) Gravity
- c) A magnet picking up a paperclip
- b) Opposes motion
- c) Shape
- d) Balanced
- c) Newton (N)
- c) Increase their speed
- c) A grassy field
- T
- F (Gravity is a non-contact force.)
- F (Balanced forces result in no change in motion.)
- T
- F (A stronger push will make it travel farther.)
- T
- T
- F (Forces like squeezing or crushing change an object's shape.)
- F (Friction helps us walk and stop cars.)
- F (Gravity is pulling it down and the surface is pushing it up. These are balanced forces.)
Part B: Subjective Questions
- Unbalanced forces are forces of unequal strength acting on an object. When applied, they cause a change in the object's motion (it starts moving, stops, speeds up, slows down, or changes direction).
- Example 1: Friction between our shoes and the ground allows us to walk without slipping. Example 2: Friction in a car's brakes helps it to slow down and stop.
- A contact force requires objects to be physically touching (e.g., pushing a door). A non-contact force can act on an object from a distance (e.g., gravity pulling a ball to the ground).
- A force can: 1. Start a stationary object moving. 2. Stop a moving object. 3. Change the speed or direction of a moving object. 4. Change the shape of an object.
- A feather falls more slowly because it has a larger surface area relative to its weight, so it is affected more by air resistance, which is a force that pushes upwards against falling objects.
- The two main forces are friction (from the grass/ground) and air resistance.
- Gravity is a non-contact force that attracts objects with mass towards each other. On Earth, it pulls everything towards the planet's center. Yes, it affects all objects with mass.
- You can reduce friction by making the surfaces smoother or by using a lubricant like oil or grease.
- When the rider applies the brakes, a frictional force is created between the brake pads and the wheel. This strong opposing force acts against the bicycle's forward motion, causing it to slow down and stop.
- Yes, there are forces acting on the book. The force of gravity is pulling the book down, and the normal force from the table is pushing the book up. The forces are balanced, so the book does not move.
Part C: Problem-Solving Questions
- This is because static friction (the friction that keeps a stationary object from moving) is stronger than kinetic friction (the friction that acts on a moving object). It takes more force to overcome static friction and get the box moving than it does to keep it sliding.
- Yes, the boulder will move. It will move to the right. The total force is the sum of their individual forces since they are pushing in the same direction: 100 N + 80 N = 180 N to the right.
- Before the parachute opens, the main forces are gravity pulling the paratrooper down and a small amount of air resistance pushing up. Gravity is much stronger, so they accelerate and fall fast. After the parachute opens, the large surface area of the parachute dramatically increases the force of air resistance pushing up. This upward force now opposes gravity much more effectively, slowing the paratrooper's descent to a safe speed.
- Car B, with the rubber wheels, will stop first. The rubber wheels and their treads are designed to create more friction than the smooth plastic wheels of Car A. The higher friction between Car B's wheels and the carpet will slow it down and stop it more quickly.
- Gate does not move: The gate would not move if the force you are applying is exactly equal to the force of the wind pushing back. The forces would be balanced, resulting in no change in the gate's motion.
Gate closes: You would be able to close the gate if the force you apply is greater than the force of the wind. The forces would be unbalanced, and the net force would be in the direction you are pushing, causing the gate to move and close.