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YR 10 PHYSICS, ENG AND COMM > Collisions and energy transfer > Flashcards

Collisions and energy transfer Flashcards

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1
Q

What is energy?

A

Energy is the ability to do work

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2
Q

Can energy be transferred from one object to another? Can it be transformed from one form to another?

A

Yes, it can do both these things

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3
Q

What is Kinetic Energy?

A

Kinetic energy is the energy an object has due to motion. The larger the mass of an object, the greater the KE. The faster the object is travelling, the greater the KE.

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4
Q

What is the formula for Kinetic Energy?

A

Kinetic Energy = 1/2 x mass x velocity squared

KE = 1/2 x m x v^2

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5
Q

What is the SI unit for Kinetic Energy?

A

Joules.

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6
Q

how many joules in a kilojoule?

A

1000 joules

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7
Q

Kinetic energy depends on the object’s mass and its speed. True / False?

A

True

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8
Q

What is Gravitational Potential Energy?

A

GPE is the energy that is related to gravitational force (gravity)

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9
Q

The larger the mass and height, the more GPE the object gains. True / False?

A

True

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10
Q

What is the formula for GPE? (Gravitational Potential Energy)

A

GPE = Mass x gravity x height

GPE = m x g x h

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11
Q

What is the SI unit for GPE? What is gravity on earth?

A

Joules

gravity is 9.8 meters per second squared

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12
Q

What is elastic potential energy? (EPE)

A

EPE is the potential energy stored as a result of applying a force to deform an elastic object

Elastic potential energy, which is the energy stored in something when you push, pull, or force it out of shape

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13
Q

Is bouncing a ball an example of elastic potential energy? (Explain) What other types of energy is involved?

A

Yes. as the ball hits the ground, it compresses and stores elastic energy. This energy returns when the ball expands again and is propelled upwards into the air

Bouncing a ball includes EPE, GPE, and KE

Small amount of sound and heat energy as well

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14
Q

What is the formula for Elastic Potential Energy? What is the SI unit for EPE?

A

EPE = 1/2 x spring constant x (extension or compression squared)

EPE = 1/2 kx^2

where:
k is the spring constant (measure of how stiff the object is. Measured in units of Newtons per meter. N/m)
x is the extension or compression (in meters)

EPE is in JOULES

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15
Q

What is the law of conservation of energy?

A

The law of conservation of energy states that energy cannot be created nor destroyed.

Whenever energy is transformed from one form into other forms, the total energy of the system is always constant because extra energy cannot be created nor can energy be destroyed.

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16
Q

How can you calculate energy efficiency?

A

Energy efficiency = amount of usable final energy / amount of initial energy x 100

(express as a percentage)

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17
Q

Can energy be transferred to the surroundings? What type of energy is it transformed into?

A

Yes, it transforms into heat energy. It is transferred to the surroundings and is extremely difficult to reuse and is often considered ‘lost’

Heat energy generally results in a rise of temperature

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18
Q

When is work considered to be ‘done?’

A

Work is done whenever things are moved or rearranged by force. The amount of work done depends on the size of the force and the distance over which the force acts. The larger the force acting, the greater the work done

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19
Q

Are work and energy scalar quantities?

A

YES.

20
Q

Are work and energy scalar quantities or vector quantities?

A

YES.

WORK IS A SCALAR QUANTITY AND ENERGY IS ALSO A SCALAR QUANTITY

21
Q

The change in the amount of Kinetic energy is equal to the amount of work done? True/False?

A

True

22
Q

What is the formula for work? A heavy object takes a force of 200 Newtons to move it 3 meters. How much work is done?

A

Work = Force applied x distance moved

W = F x d

Thus, since W =F x d, Work = 200 Newtons x 3m = 600 Joules.

23
Q

What is the SI unit for work?What is work?

A

Work is measured in joules. Work is a measure of energy transfer that occurs when an object is moved by an external force.

Work is done whenever things are moved or arranged by force.

24
Q

What is a seat belt and why is it used? How does it reduce the effect of collision?

A

Seat belts reduce the force on you as the car changes speed and direction. They also reduce the force on you by slowing you down over a larger distance when they stretch. As the seatbelt stretches, you slow down over a larger distance and therefore your acceleration is less. According to Newton’s second law, when a net force acts on a mass, it changes direction or velocity – which means it accelerates. Since F = ma, if the acceleration is less, then the force is less. Less force means less work is done and means there are fewer injuries in the crash, because you have a seatbelt on

25
Q

State what momentum is, the SI units of it and what it is measured by. What is the formula for momentum?

A

Momentum is the product of mass and velocity, and it is a vector quantity. According to Newton’s second law of motion, the rate of change of momentum is directly proportional to the force acting on the object (since velocity changing means acceleration and thus F = ma)

p = m x v or p = mv

Where p is momentum
Momentum = mass x velocity

26
Q

Whenever objects interact, energy is transformed and transferred. True / False?

A

True

27
Q

When a ball is struck by a bat, the bat has kinetic energy. In the moment where the ball hits the bat, the ball is compressed during its impact and energy is transformed into EPE within the ball.

A

fax

28
Q

Why is the conversion between kinetic energy and elastic potential energy never 100% efficient?

A

Because some energy is converted into sound, which is why you hear the collision. Some energy is also converted into the motion of particles, which results in a rise of temperature.

A machine such as ‘Hot spot’ is used in cricket to detect whether the bat has hit the ball or not. It uses infrared cameras to see the rise in temperature due to a collision. If the bat hits the ball, a brighter colour which indicates high temperatures remains on the bat.

29
Q

Once a ball is compressed by its maximum amount during a collision, it begins to spring back to its normal shape. The compressed ball exerts a force on the object that compressed it. The EPE is converted into KE. The ball moves away from the bat, racquet, club, foot or hand at a new speed and/or direction.

A

true

30
Q

When a player in sports like rugby is tackled, the Kinetic Energy the players have is sometimes transformed into physical damage since ‘work’ is done. Body parts are compressed, blood vessels are ruptured and bones are broken

A
31
Q

Even non contact sports involve collisions, forces and many resulting injuries.

A
32
Q

Why is energy never 100% efficient?

A

There is always at least some amount of energy that is transformed into heat energy and thus transferred to the surroundings. These are very difficult to reuse and is often considered as lost. This energy is transferred to the movement of particles specifically, which we could theoretically measure as a rise in temperature.

33
Q

Describe the motion of a ball bouncing

A

When a ball is in your hand and you drop it towards the ground, the gravitational potential energy from the height of the ball is transformed into kinetic energy because of acceleration due to gravity. The ball would continue to drop to the ground due to gravity until it touches the surface of the ground - where normal force will act on the ball and cause the ball to decelerate as it deforms. As it does this, the ball converts its kinetic energy to elastic potential energy, and causes the ball to bounce after its maximum deformation. This elastic potential energy is then transformed back to kinetic energy and makes the ball move back up. However, the ball does not go up to its original height, because some energy is lost or transferred tot he surroundings as thermal or sound energy.

34
Q

When or how can kinetic energy increase, regarding objects?

A

The larger the mass of an object, the greater the kinetic energy
The faster the object is travelling, the greater the kinetic energy

35
Q

The larger the mass or larger the height, the more gravital potential energy it has. True or False?

A

True

36
Q

What is the formula for elastic potential energy?

A

EPE = 1/2 x spring constant x compression squared

EPE = 1/2 x Kx^2

where k is the spring constant; a measure of how stiff the object is.

‘K’ is measured in units of NEWTONS PER METER

37
Q

What is the formula for work?

A

Work = force applied x distance moved

W = F x d

38
Q

What is the purpose of crumple zones on cars?

A

These zones are designed to crumple evenly during a car crash to absorb the energy of the collision, keeping the passenger area more intact and undamaged

39
Q

Is weight a vector quantity and if so why? What about scalar?

A

Weight the is the force of gravity acting upon an object. Force is a vector quantity making weight also a vector quantity. Mass is scalar.

40
Q

Do bearings or compass directions take priority?

A

Bearings always take priority when writing direction

41
Q

If two objects have different masses and they fall down from the same height? Which will fall faster? Why?

A

Two objects with different masses but dropped from the same height, will STILL FALL AND HIT THE GROUND AT THE SAME TIME. (Acceleration due to gravity is the same for ALL objects)
This is because they are both under the influence of gravity (9.8 meters per second squared) They also have the same height. While they may have different forces acting on the object, they will have the same acceleration which is -9.8 meters per second squared towards the earth

An example of dropping a bowling ball and a feather is different, due to the presence of air resistance - since a feather has a wider and bigger surface area than a bowling ball, causing it to sway from side to side

42
Q

9.8 meters per second squared is the value for acceleration due to gravity on earth. But what does this value mean?

A

9.8 meters per second squared, means that an object is increasing its velocity by 9.8 every second. If an object is moving up, then it is against gravity and thus is -9.8 meters per second dquared

(It is compounding eveyr second)

43
Q

What is acceleration due to gravity? Is it always negative?

A

YES. ACCELERATION DUE TO GRAVITY IS ALWAYS NEGATIVE. THEREFORE, -9.8 METERS PER SECOND SQUARED

44
Q

What does a force cause on an object? What does it change?

A

It changes the direction of the object, the speed or the shape of the object

45
Q

What is the direction of weight?

A

Weight is ALWAYS A DOWNWARD DIRECTION

It is a vector quantity and measured in Newtons with a downward direction. (Weight = mass x gravity due to acceleration)

w = m x g

YR 10 PHYSICS, ENG AND COMM (9 decks)

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