Momentum is a ______ quantity, so it can be positive or negative depending on the object's ______ .

Momentum is a vector quantity, so it can be positive or negative depending on the object's direction .

True or False? An object with a larger mass always has more momentum than an object with a smaller mass.

False. Momentum depends on both mass and velocity , so a smaller, faster object can have the same or greater momentum than a larger, slower one.

Define the principle of conservation of momentum .

The total momentum before an interaction is equal to the total momentum after the interaction, provided no external forces act on the objects.

What two types of interaction does the conservation of momentum apply to?

A collision , where two objects collide, and an explosion , where a stationary object separates into two or more parts.

Define force in terms of momentum.

Force can be described as the rate of change of momentum of an object.

For a given change in momentum, how does increasing the contact time of a collision affect the force experienced?

It decreases the force, since force and time are inversely proportional for a given change in momentum.

For a given change in momentum, force and time are ______ proportional to each other.

For a given change in momentum, force and time are inversely proportional to each other.

True or False? For a given change in momentum, a shorter contact time results in a smaller force.

False. A shorter contact time results in a larger force, since force and time are inversely proportional.

Why is the final velocity given a negative value when a car rebounds off a wall?

Velocity is a vector , so a change in direction after the collision is represented by a negative sign , opposite to the car's initial direction of travel.

Define Newton's third law of motion.

Whenever two objects interact, the forces they exert on each other are equal in magnitude and opposite in direction .

State the three rules used to identify a Newton's third law pair of forces.

The two forces act on different objects ; they are equal in magnitude and opposite in direction ; and they are always the same type of force (e.g. both weight).

Newton's third law pairs act on ______ objects, and are always the ______ type of force.

Newton's third law pairs act on different objects, and are always the same type of force.

True or False? The weight and the normal contact force acting on a book resting on a table are a Newton's third law pair.

False. Both forces act on the same object (the book) and are different types of force, so this is an example of Newton's first law , not the third.

Give an everyday example of Newton's third law.

Walking: the foot pushes backwards on the ground , and the ground pushes forwards on the foot with an equal and opposite force.

Why does increasing the contact time of a collision reduce the force of impact on a person?

Since force is the rate of change of momentum , increasing the contact time over which the same change in momentum occurs reduces the force .

Define crumple zones .

Sections at the front and back of a vehicle designed to crush or crumple in a controlled way during a collision, increasing the contact time and lowering the impact force on passengers.

Name three vehicle safety features that reduce the force of impact on passengers.

Seat belts , airbags and crumple zones .

How do seat belts reduce the risk of injury in a collision?

They stretch slightly , increasing the time taken for the passenger's momentum to reach zero, which reduces the force on the passenger.

Crash mats are thick and soft, which ______ the contact time of a landing, thereby ______ the impact force.

Crash mats are thick and soft, which increases the contact time of a landing, thereby decreasing the impact force.

True or False? A collision involving a large mass travelling at high speed only needs a short contact time to safely reduce the impact force.

False. A large mass and high speed produce a large change in momentum , so a long contact time is needed to sufficiently reduce the force.

Why might a child safely use a thinner crash mat than an adult for the same activity?

A child has a lower mass , so a smaller change in momentum, meaning less contact time increase is needed to reduce the impact force safely.

IGCSEPhysicsEdexcelPhysics (Modular)Unit 1Flashcards1. Forces & MotionMomentum

Momentum (Edexcel IGCSE Physics (Modular): Unit 1): Flashcards

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Define momentum.

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Cards in this collection (28)

Define momentum.
Momentum is the product of an object's mass and velocity: $p = m v$
State the equation for calculating momentum, defining each symbol.
$p = m v$
Where p = momentum (kg m/s), m = mass (kg), v = velocity (m/s).
Why does a stationary object have zero momentum?
Since $p = m v$ , if velocity v = 0, then momentum p must also equal zero.
Momentum is a ______ quantity, so it can be positive or negative depending on the object's ______.
Momentum is a vector quantity, so it can be positive or negative depending on the object's direction.
True or False?
An object with a larger mass always has more momentum than an object with a smaller mass.
False.
Momentum depends on both mass and velocity, so a smaller, faster object can have the same or greater momentum than a larger, slower one.
Define the principle of conservation of momentum.
The total momentum before an interaction is equal to the total momentum after the interaction, provided no external forces act on the objects.
What two types of interaction does the conservation of momentum apply to?
A collision, where two objects collide, and an explosion, where a stationary object separates into two or more parts.
Define force in terms of momentum.
Force can be described as the rate of change of momentum of an object.
State the equation relating force to change in momentum, defining each symbol.
$F = \frac{m v - m u}{t}$
Where F = resultant force (N), m = mass (kg), v = final velocity (m/s), u = initial velocity (m/s), t = time (s).
For a given change in momentum, how does increasing the contact time of a collision affect the force experienced?
It decreases the force, since force and time are inversely proportional for a given change in momentum.
For a given change in momentum, force and time are ______ proportional to each other.
For a given change in momentum, force and time are inversely proportional to each other.
True or False?
For a given change in momentum, a shorter contact time results in a smaller force.
False.
A shorter contact time results in a larger force, since force and time are inversely proportional.
A ball's momentum changes by 0.5 kg m/s over a contact time of 0.1 s. Calculate the force acting on the ball.
$F = \frac{Δ p}{t} = \frac{0.5}{0.1} = 5.0 N$
Why is the final velocity given a negative value when a car rebounds off a wall?
Velocity is a vector, so a change in direction after the collision is represented by a negative sign, opposite to the car's initial direction of travel.
Define Newton's third law of motion.
Whenever two objects interact, the forces they exert on each other are equal in magnitude and opposite in direction.
State the three rules used to identify a Newton's third law pair of forces.
The two forces act on different objects; they are equal in magnitude and opposite in direction; and they are always the same type of force (e.g. both weight).
In a collision between trolley A and trolley B, how does the force trolley A exerts on trolley B compare with the force trolley B exerts on trolley A?
They are equal in magnitude and opposite in direction: $F_{B - A} = - F_{A - B}$
Two trolleys of unequal mass collide. Are their accelerations equal? Explain.
No. From $F = m a$ , since the forces on each trolley are equal but the masses are different, the accelerations must be unequal.
Newton's third law pairs act on ______ objects, and are always the ______ type of force.
Newton's third law pairs act on different objects, and are always the same type of force.
True or False?
The weight and the normal contact force acting on a book resting on a table are a Newton's third law pair.
False.
Both forces act on the same object (the book) and are different types of force, so this is an example of Newton's first law, not the third.
Give an everyday example of Newton's third law.
Walking: the foot pushes backwards on the ground, and the ground pushes forwards on the foot with an equal and opposite force.
Why does increasing the contact time of a collision reduce the force of impact on a person?
Since force is the rate of change of momentum, increasing the contact time over which the same change in momentum occurs reduces the force.
Define crumple zones.
Sections at the front and back of a vehicle designed to crush or crumple in a controlled way during a collision, increasing the contact time and lowering the impact force on passengers.
Name three vehicle safety features that reduce the force of impact on passengers.
Seat belts, airbags and crumple zones.
How do seat belts reduce the risk of injury in a collision?
They stretch slightly, increasing the time taken for the passenger's momentum to reach zero, which reduces the force on the passenger.
Crash mats are thick and soft, which ______ the contact time of a landing, thereby ______ the impact force.
Crash mats are thick and soft, which increases the contact time of a landing, thereby decreasing the impact force.
True or False?
A collision involving a large mass travelling at high speed only needs a short contact time to safely reduce the impact force.
False.
A large mass and high speed produce a large change in momentum, so a long contact time is needed to sufficiently reduce the force.
Why might a child safely use a thinner crash mat than an adult for the same activity?
A child has a lower mass, so a smaller change in momentum, meaning less contact time increase is needed to reduce the impact force safely.

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