Physics Flashcards
What do the letters in SUVAT stand for?
S = displacement U = initial velocity V = Final velocity A = acceleration T = time
What can be calculated by finding the area under a velocity-time graph?
Displacement
What does the gradient of a displacement-time graph provide you?
The velocity at that point.
On a piece of ticker tape, the dots are getting closer together. What can you say about the motion of this object?
It is slowing down.
Name the three things that car designers include in a car to protect you in a crash.
seat belts
air bags
crumple zones
How do seat belts, crumple zones and air bags protect you in a crash?
These features reduce injuries to the people in the car by absorbing energy from the impact. They increase the time taken for the change in momentum on the occupants’ bodies, and so reduce the forces involved and any subsequent injuries.
These features absorb energy when they change shape. This reduces injuries to the people in the car. They increase the time taken for the change in momentum on the occupants’ bodies, and so reduce the forces involved and any subsequent injuries.
How do seat belts reduce injuries in a crash?
Seat belts stop you tumbling around inside the car if there is a collision. However, they are designed to stretch a bit in a collision. This increases the time taken for the body’s momentum to reach zero, and so reduces the forces on it.
How do air bags reduce injuries in a crash?
Air bags increase the time taken for the head’s momentum to reach zero, and so reduce the forces on it. They also act a soft cushion and prevent cuts.
How do crumple zones reduce injuries in a crash?
Crumple zones are areas of a vehicle that are designed to crush in a controlled way in a collision. They increase the time taken to change the momentum of the driver and passengers in a crash, which reduces the force involved.
What is Newtons third law?
Newton’s Third Law of Motion concerns equal and opposite forces. It states that: “If A exerts a force on B, then B exerts an equal but opposite force on A”.
Forces always occur in ‘Newton pairs’ and are made up from an action force and an equal reaction force in the opposite direction.
Describe the concept of conservation of momentum?
As long as no external forces are acting on the objects involved, the total momentum stays the same in explosions and collisions. We say that momentum is conserved.
You can use this idea to work out the mass, velocity or momentum of an object in an explosion or collision.
What is momentum?
A moving object has momentum. This is the tendency of the object to keep moving in the same direction. It is difficult to change the direction of movement of an object with a lot of momentum.
Describe Newtons first law.
According to Newton’s first law of motion, an object remains in the same state of motion unless a resultant force acts on it. If the resultant force on an object is zero, this means:
- a stationary object stays stationary
- a moving object continues to move at the same velocity (at the same speed and in the same direction)
Describe Newtons second law.
Newton’s second law of motion can be described by this equation:
resultant force = mass × acceleration
F = m x a
This is when:
- force (F) is measured in newtons (N)
- mass (m) is measured in kilograms (kg)
- acceleration (α) is measured in metres per second squared (m/s2)
The equation shows that the acceleration of an object is:
- proportional to the resultant force on the object
- inversely proportional to the mass of the object
In other words, the acceleration of an object increases if the resultant force on it increases, and decreases if the mass of the object increases.
How does a pendulum demonstrate the conservation of energy (KE and GPE)?
The pendulum is a simple machine for transferring gravitational potential energy to kinetic energy, and back again.
When the bob is at the highest point of its swing, it has no kinetic energy, but its gravitational potential energy is at a maximum. As the bob swings downwards, gravitational potential energy is transferred to kinetic energy, and the bob accelerates.
At the bottom of its swing, the bob’s kinetic energy is at a maximum and its gravitational potential energy is at a minimum.
As the bob swings upwards, its kinetic energy is transferred to gravitational potential energy again. At the top of its swing, it once again has no kinetic energy, but its gravitational potential energy is at a maximum.
