Dynamics (Kinematics)

Question 1

Displacement (s)

Answer 1

Distance moved from a point in given direction. It is a vector.

Question 2

Velocity (v), and its equation

Answer 2

The rate of change of displacement with time. It is a vector. Equation = change in speed/ time.

Question 3

Acceleration (a), and its equation and units

Answer 3

The rate of change of velocity with time. It is a vector. Its units are ms^-2. Equation = change in velocity/ time.

Question 4

Uniform acceleration

Answer 4

Uniform acceleration is where the velocity of an object moving along a straight line changes at a constant rate. (the acceleration is constant).

Question 5

Non-uniform acceleration

Answer 5

Non-uniform acceleration is where the direction of the motion of an object changes, or its speed changes, at a varying rate.

Question 6

When can Suvat be used

Answer 6

When acceleration is constant

Question 7

What does Suvat stand for

Answer 7

s- displacement
u- initial velocity
v- final velocity
a- constant acceleration
t- time

Question 8

Acceleration due to gravity

Answer 8

For something under freefall assuming no air resistance: F=ma so mg=ma g=a

Question 9

Ball Bearing Freefall Method RP

Answer 9

Method
When the current to the magnet switches off, the ball drops and the timer starts
When the ball hits the trapdoor, the timer stops
Measure distance with metre ruler

Question 10

S=ut+1/2at^2 graph analysis

Answer 10

Straight line graph through origin of speed against time^2 graph
Gradient= 1/2a

Question 11

Vertical Projectiles

Answer 11

When projectile is thrown vertically upwards
Use Suvat
choose upwards as positive direction
a= -9.81
at highest point v=0

Question 12

Horizontal Projectiles

Answer 12

Where projectile is projected perpendicular to the vertical
Does not affect vertical motion
Think of vertical and horizontal components separately.

Question 13

Solving Horizontal Projectile

Answer 13

1, draw diagram
2, consider vertical first (downwards positive)
3, suvat (a= 9.81)
4, then horizontal use. s= d/ t

Question 14

Non-Horizontal projectiles

Answer 14

1, draw diagram
2, find initial velocities even if unknown variables (trig or pythag)
3, vertical direction (a= -9.81, u= vertical side, top of curve v= 0, end of curve v= -u, s=0
4, horizontal direction s= d/t

Question 15

Effect of air resistance on a falling object

Answer 15

At instant of release- 0 speed so 0 AR (a=g=9.81)
Later- speed increased so AR increased, resultant force down so a down
Eventually- AR increases until equal to weight, resultant force= 0, so a=0 and v is constant (terminal velocity).

Question 16

Drag force

Answer 16

The resistive force on an object when it moves through a fluid. None when stationary. Size of force increases as velocity increases.

Question 17

Lift

Answer 17

An upwards force on an object moving through a fluid. Force acts at right angles to the velocity of the fluid. Comes about when the object is shaped to change the direction of the fluid flow around it (a wing).

Question 18

Two factors that affect the maximum speed of a car

Answer 18

1, size of thrust (greater thrusts can reach higher speeds before it equals drag)
2, streamlining of the car (drag reduced, car can reach faster speeds)