The three laws of motion, inertia, terminal velocity, and the factors affecting thinking distance, braking distance and stopping distance.
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1.State Newtons first law.
If the resultant force on an object is zero, a stationary object stays still and a moving object continues at the same velocity.
2.What is inertia?
The tendency of an object to continue in its state of rest or of uniform motion.
3.What is inertial mass?
A measure of how difficult it is to change the velocity of an object, found from force divided by acceleration.
4.State Newtons second law.
The acceleration of an object is proportional to the resultant force and inversely proportional to its mass.
5.State the equation for Newtons second law.
resultant force = mass x acceleration
6.A 1200 kg car accelerates at 2 m/s squared. Calculate the resultant force.
1200 x 2 = 2400 N.
7.A 500 N force acts on a 100 kg object. Calculate the acceleration.
500 divided by 100 = 5 m/s squared.
8.What happens to acceleration if mass doubles for the same force?
It halves, because acceleration is inversely proportional to mass.
9.State Newtons third law.
Whenever two objects interact, the forces they exert on each other are equal and opposite.
10.Why do the two forces in Newtons third law not cancel out?
They act on different objects, so they cannot be added together as a resultant on one object.
11.Give an example of Newtons third law.
When you push on a wall, the wall pushes back on you with an equal and opposite force.
12.What is terminal velocity?
The maximum constant velocity reached by a falling object, when the resultant force becomes zero.
13.Explain how terminal velocity is reached.
At first weight exceeds air resistance so the object accelerates. As speed increases air resistance grows until it equals weight, the resultant force is zero, and the object falls at constant velocity.
14.What happens to a skydiver when the parachute opens?
Air resistance increases sharply and exceeds weight, so the skydiver decelerates until a new lower terminal velocity is reached.
15.What shape is a velocity-time graph for an object reaching terminal velocity?
A curve that gets less steep, then flattens into a horizontal line.
16.What is stopping distance?
The sum of the thinking distance and the braking distance.
17.What is thinking distance?
The distance travelled during the reaction time, before the brakes are applied.
18.What is braking distance?
The distance travelled while the braking force is slowing the vehicle to a stop.
19.Give three factors that increase thinking distance.
Tiredness, alcohol or other drugs, distractions, and higher speed.
20.Give four factors that increase braking distance.
Wet or icy roads, worn tyres, worn brakes, and higher speed.
21.What is a typical human reaction time?
Between 0.2 and 0.9 seconds.
22.How does speed affect braking distance?
Braking distance increases much faster than speed, because the kinetic energy depends on speed squared.
23.What happens to the kinetic energy of a car when it brakes?
Work is done against friction, transferring energy to the thermal store of the brakes.
24.Why is a large deceleration dangerous?
It requires a very large braking force, which can cause the brakes to overheat and the vehicle to skid.
25.In the required practical on acceleration, what is investigated?
How the acceleration of a trolley changes with the force applied or with its mass.
26.How is the acceleration measured in that practical?
Using light gates and a data logger, or by recording distance and time and calculating.
27.What would a graph of acceleration against force look like?
A straight line through the origin, showing direct proportion.
28.What would a graph of acceleration against mass look like?
A curve falling away, since acceleration is inversely proportional to mass.
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