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CP2H
GCSE Combined Science Physics
Question | Answer |
---|---|
What is a vector quantity | A quantity that had a magnitude and direction |
Give two examples of vectors | Force, acceleraration, velocity, displacement |
Diefine a resultunt force | The total force that results from 2 or more forces acting on an object |
If an object is at rest or moving at a steady velocity, what can you say about the forces acting on it? | They are balanced |
If the force on an object are balanced, what is the resultant force? | 0 N |
If the forces on an object are balanced, what are the 2 possible ways it could be in motion? | Stationary or moving with a constant velocity |
If the forces on an object are unbalanced, what are the 2 possible ways it could be in motion? | Accelerating or decelerating |
What is Newton's first law of motion ? | An object will remain at rest or move with a constant velocity unless an external force acts on it |
What affect do balanced forces have on the motion of an object? | Balanced forces do not change the motion of an object. |
What affect will unbalanced forces have on the motion of an object? | Unbalanced force will change speed and/or direction of an object or change the velocity of the object |
What happens to the velocity of an object if it moves in a circle ? | The velocity changes as the direction is constantly changing |
What is the name of the force that causes objects to move in circles? | Centripetal forces |
In which direction does the centripetal force point? | It is towards the center of the circle. |
What is the centripetal force that keeps the planets orbiting the Sun? | Pull of graviry |
What is the centripetal force that keep cars turning around a roundabout? | Friction between the road and the tyres |
What is the force that the keeps the riders moving in a circle? | Tension in the cables. |
How can an object have a constant speed when moving in a circle? | Speed is a scaler and the direction does not matter. |
Define mass ? | Mass is the quantity of matter there is in an object |
What unit is in mass mesured in ? | Kilogram |
What measuring instrument measures mass? | Scales or balance |
Define weight ? | A measure of the pull of gravity on an object. |
What units is it measured in? | N or Newtons |
What measuring instrument measures weight? | Forcemeter or newtonmeter. |
What is the equation that allows you to calculate the weight W of a mass m? | W = m X g |
A 200kg mass land on a moon where g= 2N/kg Calculate its weight. | W= mx g = 200 x 2 = 400N |
What does g stand for ? | Gravitational field constant. |
When you drop a feather on earth, what are the 2 forces acting on it? | Weight and air resistance. |
What are the units of velocity? | m/s |
A car goes from travelling at 10m/s to 20m/s in 2 seconds what is its acceleration? | 5m/s/s |
What are the units of acceleration? | 2m/s/s |
Describe the motion of this object and calculate the acceleration: | No motion for first 3 seconds Constant acceleration of 4m/s/s from 3 to 5 seconds Constant velocity of 8m/s between 5 and 8 seconds Deceleration of 4m/s/s from 8 to 10 seconds |
What are the units of force? | Newtons |
What is the resultant force? | The overall force on an object |
What is the resultant force on this object: | 200N-100N=100N |
What is the acceleration of the car if its mass is 500kg? | a=F/m=100/500=0.2 m/s/s |
Define acceleration | Rate of change of velocity |
What is Newton’s 2nd Law? | Net force= mass x acceleration |
What is acceleration? | How much velocity changes. |
What two factors affect the acceleration of an object? | Force applied and mass of object. |
What is the equation that links force, mass and acceleration ? | Force = Mass X Acceleration. |
What is inertial mass (H) ? | Force divided by the acceleration that the force produces |
What force is needed for a mass of 3kg to accelerate at 5m/s/s? | F=mxa = 3 x 5 =15N |
What force is needed for a mass of 10kg to accelerate at 10m/s/s? | F=mxa = 10 x10 =100N |
If a force of 12 N is applied to a 4kg mass, what is its acceleration? | a =F/m= 12/4=3N |
If a force of 10 N is applied to a 2kg mass, what is its acceleration? | a=F/m=10/2=5m/s/s |
What force is needed for a mass of 0.5 kg accelerates at 2m/s/s? | F= mxa = 0.5 x 2 =1N |
10 What force is needed for a mass of 0.4 kg accelerates at 6m/s/s? | F=mxa = 0.4 x 6= 2.4N |
What is momentum a measure of? | It is a measure of the tendency of an object to keep moving, or how hard it is to stop it moving |
What does the momentum of an object depend upon? | It depends on the mass and velocity of the object |
What is the equation for momentum ? | In words and symbols Momentum = mass x velocity p=mxv |
What units do we measure momentum in? | Kg m/s |
How is the force acting on an object related to the change in momentum? | Force = change in momentum/time |
What is this equation in symbols | F = (mv-mu)/t |
What is the principle of conservation of momentum? | The total momentum is the same before the collision as it is after the collision providing no external forces act. |
An object has a mass of 100g and is moving at 2m/s. What is its momentum? | Momentum = mass x velocity = 100 x 2 = 200kgm/s |
What force is need to change a 10kg object from 10 m/s to 20 m/s in 5 seconds? | F = (mv-mu)/t = (10 x 20-10x10)/5 = (200-100)/5 = 100/5= 20N |
If the momentum of 2 cars =2000kgm/s before the collision when they get stuck together, the total mass of the cars is 100kg, what is the final velocity of the cars? | Total initial momentum before collision = total momentum after the collision 2000 = m x v 2000= 1000 x v V=2m/s |
Define thinking distance | The distance travelled by a vehicle while the driver reacts |
Define braking distace | The distance travelled by a vehicle while the brakes are working to bring it to a halt. |
Define overall stopping distance | Thinking distance + braking distance |
How can thinking distance be calculated? | Thinking distance = speed x reaction time |
Name two factors that can increase thinking distance | Speed, Alcohol, drugs, tiredness, use of mobile phone |
Name 2 factors that can increase braking distance | speed, worn brakes. Icy road conditions, worn tyres |
What provides the centripetal force when a)the moon orbits the earth b) London Eye | Friction |
What happens to thinking distance car speed doubles from 20mph to 40mph? | It increases by a factor of 4 |
What happens to the braking distance if the car speed doubles from 20mph to 40mph? | It doubles |
What happens to thinking distance, braking distance if the road is icy? | Thinking distance same, braking distance increases |
What happens at terminal velocity? | Weight and Air resistance are balanced. The resultant force is zero and the parachutist does not accelerate |
What is thinking distance? | The distance a car travels from the driver seeing a hazard to the driver pressing the brake |
What is braking distance? | The distance a car travels from the driver pressing the brake to the car stopping |
What is stopping distance? | Thinking+braking distance The distance the car travels from the driver seeing the hazard to coming to a stop |
Give three factors that increase braking distance | Poor condition of brakes, icy roads, heavy car |
Give three factors that increase thinking distance | Distractions in the car (Eg music mobile phones etc) Tiredness, drugs, alchohol |
Which way is the force in circular motion? | Towards the centre of the motion |
If a object rotates at constant speed is it accelerating? Why? | Yes- as velocity includes a direction and the direction is changing hence acceleration |
What provides the centripetal force when a)the moon orbits the earth b) London Eye | Gravity b) Tension in the wires |
Give the units of energy | Joules |
What is power? | The rate at which work is done |
What are the units of power | Watts |
What is another word for work done | Energy Transferred |
When does an object gain Gravitational Potential Energy? | When it is raised in a gravitational field |
What is momentum? | A measure of how hard it is to stop an object |
What is a negative acceleration? | Deceleration |
.What is the force during a crash greater if the car is moving faster? | It has a greater deceleration so there is a greater force on the vehicle. From Newton’s second law F=m x a |
Why is there a greater force on a lorry travelling at the same speed before crashing than a car? | Greater mass means a greater force form Newton’s second law F=m x a |
What are crumple zones? | They are areas of the car that crumple easily e.g. front and back |
How do crumple zones protect the car and passengers? | They take a little time to crumple in a collision, so the deceleration of the car is less, so there is less force than if that part of the car was solid and stopped instantly. |
How would you move if you were not wearing a seat belt and the car braked suddenly? | You would continue to move forward until you collided with something e.g windows, steering wheel |
What do air bags work? | They increase the time taken for a persons head to stop in a collision, reducing the deceleration so reducing the force. |
How do seat belts work? | They increase the time taken for a persons to stop in a collision as they stretch slightly, reducing the deceleration so reducing the force. |
What is the equation that links force and momentum? | Force =(mv-mu)/t |
Why do you bend your knees when you land after jumping? | This increases the time over which you stop, so there is a lower deceleration, so there is a lower impact force. |
State the equation which links mass, momentum and velocity | ρ = mv |
What is the unit of weight? | Newtons (N) |
What is the unit of mass? | kilograms (kg) |
What is unit of gravitational field strength? | newtons per kilogram (N/kg) |
The stopping distance of a vehicle is the sum of the ….. | thinking and breaking distances |
The distance a vehicle travels while the driver is reacting is the … | thinking distance |
Sound in air travels at … | 330 m/s |
The distance a vehicle travels which the driver is breaking is the … | breaking distance |
Reaction time is… | the time it takes a driver to react |
A typical reaction time is … | 0.2-0.9 s |
Factors which influence reaction time are… | tiredness, drug, alcohol, distractions |
Fctors which affect breaking distance are … | weather conditions, conditions of breaks and tyres |
Both thinking and breaking distance are affected by which factor? | speed of vehicle |
The greater the speed of a vehicle, the _________ the force required to stop the vehicle | greater |
The distance and object moves and the direction in which it moves is known as the _________ | displacement |
State Newton's First Law | The velocity of an object will only change if a resultant force is acting on the object. |
If balanced forces act on a moving object it will … | continue to travel at a constant speed |
If balanced forces act on a stationary object it will … | remain stationary |
State Newton's Second Law | Force = mass x acceleration (The acceleration of an object is proportional to the resultant force acting on the object, and inversley proportional to the mass of the object) |
State Newton's Third Law | Whenever two objects interact, the forces they exert on each other are equal and opposite |
The tendency of objects to continue in their state of rest or of uniform motion is known as | inertia |
What is a contact force? | A force between two object which are touching |
What ia a non-contact force? | A force between objects which are separated by space. |
Give two examples of contact forces | e.g. friction, air resistance |
List three non-contact forces | gravitational, electrostatic, magnetic |
Define weight | The force ofgravity acting on an object's mass |
What device is used to measure weight? | A newtonmeter |
What is the name of the single point at which an object's mass appears to act? | centre of mass |
The center of mas of an object is… | the single point at which the objects weight appears to act. |
The single force which has the same effect as the combination of all the different forces acting on an object is the ______________ _______________. | resultant force |