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21 Cards in this Set
- Front
- Back
Reducing injury from accidents |
1) increases impact time 2) reduces the rate of change in momentum 3) less force acting on the force |
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Why is a sport car faster than a normal car? |
1) streamlined shape reduce air resistance 2) greater streamline 3) air resistance is smaller for the same speed |
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How does brake stop in terms of energy |
1) work is done by the frictional force between the brakes and the wheel 2) transferring kinetic energy to heat energy |
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Anti braking system |
Anti braking system prevents the cars to be locked and stops the car from skidding |
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Benefits of regenerative braking system |
1) battery needs charging less 2) efficency of the car increases 3) kinetic energy is not wasted |
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Explain how a car reaches a top speed[3] |
1) as speed increases, drag force increases too 2) eventually, thrust is equal drag force 3) the resultant force is now equal and there is no further acceleration |
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Terminal velocity |
1) on leaving the plane the only f9orce acting is weight 2) as parachutist falls air resistance acts upward 3) weight is greater than air resistance or resultant force acts downward 4) so parachutist accelerates 5) as velocity/speed increases so does air resistance 6) terminal velocity is reached when weight equals air resistance 7) opening parachute increases surface area 8) increases air resistance 9) air resistance is greater than weight 10) resultant force acts upwards 11) parachutists decelerates 12) lower velocity means reduced air resistance 13) air resistance and weight become weight but at a lower terminal velocity |
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Action reaction forces |
forces are equal and opposite in direction. 1) forces from the object 2) causing the object to move in a forward and opposite direction |
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Resultant force |
Is the single force that has the same effect as all other forces combined |
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What happens when the resultant force is ZERO |
1) object remain stationary 2) object move at a constant speed/velocity in a particular direction |
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What happens when object is NOT zero resultant force |
1) object will either accelerate or decelerate in the direction of the resultant force |
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String |
Elastic potential energy |
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Hookes' law |
Double the force = double the extension The extension is directly proportional to the force applied |
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The conservation of Momemtum |
The Momemtum before and after the collision is equal |
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What is meant by action reaction forces? |
The forces are equal in opposite direction |
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How to calculate the resultant force when the arrows are in the same direction? |
Add |
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How do you calculate the resultant force when the arrow are in different direction |
Subtract |
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The difference between elastic and inelastic collision |
Df |
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What is the difference between elastic and inelastic collisions |
Elastic 1) no loss of energy 2) masses bounce off 3) no external forces Inelastic inelastic 1) 2 objects stick together 2) loss of kinetic energy into heat or sound |
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Explain why the Top speed of the car is greater than the top speed of the van |
The car and the van reach the top speed when the forward force equals the drag force The drag force at any speed is smaller for the car than for the van As the car is more streamlined Therefore, the car's drag force will equal the forward force at a higher speed |
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Explain how a car or a bicycle reaches terminal velocity [6] |
1) forward force > air resistance 2) the resultant force is forward 3) So parachutist accelerate 4) as velocity increases, the air resistance increases. 5) the resultant force decreases 6) so the parachutist will decelerate. 7) eventually, weight and air resistance is equal 8) the resultant force is zero, and there would be no acceleration 9) the cyclist is moving at a constant velocity, a terminal velocity is reached. |