Dynamics Section Flashcards
What is velocity?
Rate of change of displacement
What is the definition for Conservation of energy?
Energy cannot be created or destroyed, only converted from one form to another.
What is the definition for 1 Newton?
One newton is defined as the force required to make a 1kg object accelerate at 1ms-2.
What is the resultant of a number of forces?
the single force that would have the same effect as all the other forces OR the vector sum of all the forces
Which two units can be used for momentum?
Ns OR kgms-1
Which of the following are scalars? Time, Momentum, Acceleration, Energy, Speed, Velocity, Displacement, Distance, Force
Scalars: Time, Energy, Speed, Distance
A ball is thrown upwards into the air and is allowed to fall and bounce. See graph.
Between which points on the graph is the ball travelling upwards?
A-B, E-F,
What is acceleration?
Rate of change of velocity OR change in velocity per second.
What is the difference between distance and displacement?
Distance is the length of the actual path travelled, Displacement is the straight line distance between where you started and where you finished, with a direction.
What is your weight in freefall?
0 Newtons
Explain how an object reaches it’s terminal velocity.
The weight of the object acts down towards the surface of the planet. As the object falls it accelerates, as it does this the air resistance up the way will increase as it falls faster. Eventually the weight = air resistance. This gives equal and opposite forces so the forces are balanced. This gives a constant velocity, terminal velocity.
How can an elastic collision be identified?
Calculate the total kinetic energy before the collision and the total energy after the collision.
If the total kinetic energy before the collision is equal to the total kinetic energy after the collision then it is an elastic collision.
What is gravitational field strength?
The force due to gravity per unit mass (kg)
What is Newtons First Law?
If balanced forces act on an object it will : Remain at rest or continue to travel at a constant velocity in a straight line
What would happen to your apparent weight if you were standing on a set of Newton scales and were in a lift that was accelerating downwards?
Your apparent weight would decrease, It would be equal to your weight minus the force to cause the acceleration downwards.
What is the difference between speed and velocity?
Speed is distance divided by time OR rate of chage of distance Velocity is the displacement divided by time OR rate of change of displacement, with a direction
What can be calculated from the area under a Force - time graph?
Impulse OR Change in momentum
Explain how a satellite remains in orbit.
The satellite has a constant horizontal velocity and a constant vertical acceleration due to the gravitational field strength. The planet curves away from the satellite as it falls.
What would happen to your apparent weight if you were standing on a set of Newton scales and were in a lift that was accelerating upwards?
Your apparent weight would increase, It would be equal to your weight plus the force to cause the acceleration upwards.
What would happen to your apparent weight if you were standing on a set of Newton scales and were in a lift that was de-accelerating upwards?
Your apparent weight would decrease, It would be equal to your weight minus the force to cause the de-acceleration upwards.
What is Newtons Second Law?
When an unbalanced force acts on an object it will accelerate.
A brick is dropped first onto concrete then onto a sponge surface. The same brick is dropped and it is dropped from the same height. On which surface does the brick exert the smallest force?
As the brick is dropped from the same height, it will start from rest in both cases and reach the same speed before it hits the surface. The change in momentum remains the same, mv-mu. The time of contact will increase on the spongy surface. Ft = mv-mu So the average force will decrease.
What is the definition of Conservation of momentum?
The total momentum before a collision is equal to the total momentum after a collision in the absence of external forces
Explain what would happen to your apparent weight if you were standing on a set of Newton scales and were in a lift that was travelling at a constant speed.
Your apparent weight would = real weight as the forces are balanced.
How can an inelastic collision be identified?
Calculate the total kinetic energy before the collision and the total energy after the collision.
If the total kinetic energy before the collision is greater than the total kinetic energy after the collision then it is an inelastic collision.
What causes a projectile to follow a curved path?
The projectile has a constant horizontal velocity and a constant vertical acceleration due to the gravitational field strength.
What is the definition of Impulse
Force on an object multiplied by the time the force acts for OR the change in momentum of an object.
Which of the following are vectors? Mass, Weight, Momentum, Impulse, Work, Temperature, Acceleration, Velocity, Speed
Vectors: Weight, Momentum, Impulse, Acceleration, Velocity
What quantity is always conserved in a collision?
Momentum
What is speed?
Rate of change of distance
What would happen to your apparent weight if you were standing on a set of Newton scales and were in a lift that was de-accelerating downwards?
Your apparent weight would increase, It would be equal to your weight plus the force to cause the de-acceleration downwards.
A ball is thrown upwards into the air and is allowed to fall and bounce. See graph.
At which points is the ball at the top of it’s flight?
B, F
What formula is used to work out the component of weight parallel to the slope?
F = mgsinØ
A ball is thrown upwards into the air and is allowed to fall and bounce. See graph.
Between which points on the graph is the ball hitting the ground?
C-E, G-I
What is calculated from the area under a speed-time graph?
Distance travelled
What is the difference between a vector and a scalar?
Scalar requires size / magnitude only Vector requires size / magnitude and a direction
What is calculated from the area under a velocity - time graph?
Displacement
