# Work, Energy and Momentum

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• Created by: allieal
• Created on: 24-12-13 10:55
What is work?
When a force moves an object, energy is transferred and work is done. Both energy and work are measured in Joules (J)
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How is work calculated?
Work Done (Joules, J) = Force (Newtons, N) x Distance Moved in direction of force (metres, m)
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When work is done to overcome friction, what energy is transferred?
Energy by heating
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What is gravitational potential energy?
Energy stored in an object becasue of its position in the Earth's gravitational field. When an object moves vertically its increases it's gravitational potential.
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How do you calculate the change in gravitational potential energy?
Change in gravitational potential energy (J) = Mass (kg) x Gravitational Field Strength (N/kg) x Change in Height (m)
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What is power and how is it calculated?
Power is the rate of transfer of energy. Power (Watts) = Energy (J) / Time (s)
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What do all moving objects have?
Kinetic Energy. Dependent on speed and mass
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How is kinetic energy calculated?
Kinetic Energy (J) = 0.5 x Mass (kg) x Velocity Squared (m/s)
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What is elastic potential energy?
The energy stored in an elastic object when work is done on the object
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When a spring is released what energy is released?
Kinetic Energy
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What is momentum?
Momentum (kg m/s) = Mass (kg) x Velocity (m/s)
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What happens to momentum when objects interact?
Momentum is conserved. The total momentum before the interaction is equal to the total momentum afterwards, provided there are no external forces. This law is conservation of momentum
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Similar to velocity, what does momentum have?
Both size and direction
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What happens in an explosion?
Two stationary objects move apart with equal and opposite momentum. One momentum is positive and the other negative so the total momentum after the explosion is zero.
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What is the area of car designed to fold during a collision and what does it do?
Crumple Zone. Increases impact time and reduces force on car and occupants.
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When a vehicle collides what does the force of impact depend on?
Mass,Change in Velocity and Duration of Impact
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What is the purpose of seat belts and air bags?
Spread the force across the chest and also increase impact time.
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## Other cards in this set

### Card 2

#### Front

How is work calculated?

#### Back

Work Done (Joules, J) = Force (Newtons, N) x Distance Moved in direction of force (metres, m)

### Card 3

#### Front

When work is done to overcome friction, what energy is transferred?

### Card 4

#### Front

What is gravitational potential energy?

### Card 5

#### Front

How do you calculate the change in gravitational potential energy?