Starter quiz
- How many newtons (N) are there in 2.5 MN?
- 2500
- 25,000
- 250,000
- 2,500,000 ✓
- 25,000,000
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- When two or more forces act on an object, we can imagine a single force that has the same effect as this combination of forces. This single force is called the ______ force.
- 'resultant' ✓
- A coin is dropped into a swimming pool. While the coin is falling downwards through the water, which of the following forces act on it?
- air resistance
- gravitational force ✓
- normal reaction force
- drag ✓
-
- There is a law of physics which states that forces come in equal and opposite pairs, which act between pairs of objects. What is the name of this law?
- Newton’s First Law of motion
- Newton’s Second Law of motion
- Newton’s Third Law of motion ✓
- Newton’s Fourth Law of motion
-
- Which of the following are correct definitions of acceleration?
- change in displacement divided by time taken
- rate of change of velocity ✓
- time taken to change velocity by one metre per second
- change in velocity per second ✓
-
- Which of the following situations involve a change in velocity?
- A car increases speed as it travels in a straight line. ✓
- A car travels in a straight line at a steady speed.
- A car turns a corner without changing speed. ✓
- A car slows down while turning a corner. ✓
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Exit quiz
The diagram shows four forces acting on an object. What is the magnitude of the resultant force?- 1 N ✓
- 5 N
- 6 N
- 7 N
- 13 N
-
- Which of the following is not caused by a resultant force acting on an object?
- moving at constant velocity ✓
- changing direction
- start moving
- stop moving
- decelerating and changing direction
-
- Which of the following statements are included in Newton’s First Law of motion?
- A stationary object remains stationary if there is no resultant force. ✓
- Every action has an equal and opposite reaction.
- A moving object’s velocity stays the same if no resultant force acts. ✓
- When object A exerts a force on object B, B also exerts a force on A.
-
- A ship travels at a constant speed without changing direction. Which of the following statements are correct?
- There is a steady resultant force acting on the ship.
- There is no resultant force acting on the ship. ✓
- The force pushing it forwards is equal to the force pushing it backwards. ✓
- The force pushing it forwards is greater than the force pushing it backwards.
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- A person pushes a stone across a frozen lake. After they let go, the stone slides across the ice, slowing and stopping before it reaches the other side of the lake. Why does the stone slow and stop?
- The person’s pushing force runs out.
- The person’s pushing force transfers to the thermal store.
- There is a resultant force acting in the opposite direction to the motion. ✓
- Other forces cancel out the person’s pushing force.
-
- Which of the following vans is decelerating?
Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- A single resultant force has the same effect as several forces acting on an object
- If there is no resultant force on an object, it remains still or continues to move at a steady speed in a straight line
- If there is a resultant force on an object, it will accelerate in the direction of the force
- A resultant force acting in the opposite direction to movement will decelerate (slow down) an object
Common misconception
A common belief is that a resultant force is needed to keep an object in motion, and if no resultant force acts on an object then it must be stationary.
Discuss examples in which friction is very low or absent, such as a puck sliding across an ice rink or an object being dropped during a space walk and extrapolate to what would happen if friction disappeared entirely.
Keywords
Resultant force - the effect of a set of forces on an object
Newton’s first law of motion - an object will remain at rest, or in motion in a straight line at constant speed, unless there is a resultant force acting on it
Velocity - the rate of change of displacement of an object, measured in metres per second (m/s)
Accelerate - a change in the speed and/or direction of an object
Decelerate - a decrease in the speed of an object
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