Motion with non-uniform acceleration

Question 1

What will there be when an object moves through a fluid?

Answer 1

A resistive force to it’s motion.

Question 2

How is a resistive motion created?

Answer 2

Collisions with the particles in the fluid slowing the object down.

Question 3

What factors effect the drag force? (4)

Answer 3

1) Velocity of the object.
2) Area of the object.
3) Density of the fluid the objects moving through.
4) How streamline the object is.

Question 4

As the velocity of an object increases what also increases?

Answer 4

The drag force

Question 5

What is drag force proportional to?

Answer 5

The surface area that is perpendicular to the direction of motion.

Question 6

What is drag force proportional to in relation to velocity?

Answer 6

(Velocity)^2

Question 7

How would you calculate drag?

Answer 7

(Factor change in area) x ((new speed/old speed)^2) x old drag.

Question 8

A skydiver is falling at 50ms^-1 and experiences a drag force of 750N. She deploys her parachute and begins to slwo down. The frontal area of the parachute plus the skydiver is 60 times greater than the frontal area of the skydiver. Calculate the drag force on the parachute plus skydiver when the skydiver is travelling at 10ms^-1.

Answer 8

1800N

Question 9

A skydiver experiences a dragt force of 800N before their parachute is opened. The velocity of the skydiver decreases by a factor of 6 when the parachute is opened. The total frontal area of the skydiver and open parachute is 100 times greater than before the parachute is opened. Calculate the total drag force on the skydiver and parachute system after the parachute is opened.

Answer 9

2200N

Question 10

At t=0s why is there an acceleration for an apple falling?

Answer 10

The only force acting is the weight of the apple therefore due to unbalanced forces there is an acceleration.

Question 11

A short time after t=0s describe what happens to falling apple in terms of the forces acting on it?

Answer 11

The drag force is less than the weight of the apple therefore there is a resultant force acting downwards.

Question 12

What happens before terminal velocity?

Answer 12

The apple increases in velocity therefore becomes greater drag unit the apple is in terminal velocity.

Question 13

What happens in terms of acceleration and velocity during terminal velocity?

Answer 13

There is no acceleration but there is constant velocity.

Question 14

Define a uniform gravitational field.

Answer 14

A region of space in which objects experience the same gravitational field strength.

Question 15

Define terminal velocity.

Answer 15

Maximum velocity a falling object can travel at because resistive forces equal the weight of the object.

Question 16

Define viscosity.

Answer 16

A measure of a fluids resistance to flowing.

Question 17

Define drag.

Answer 17

A frictional force opposing motion due to an object moving through a fluid, proportional to the square of the objects speed; and proportional to the surface area of the object in the plane perpendicular to the direction of motion.

Question 18

Define a fluid.

Answer 18

A fluid is a substance that can flow,including liquids and gases.

Question 19

Sketch a velocity-time graph to represent a object falling including where terminal velocity occurs.

Answer 19

See notes

Question 20

On a velocity against time graph representing a falling object where is there maximum acceleration and where is there minimum acceleration?

Answer 20

Maximum- At t=0 where the gradient is steepest and will equal g.
Minimum- Is when the object is at terminal velocity.

Question 21

There are 3 stages to terminal velocity, what is the 1st stage (just before falling) relating to: speed, drag, resultant force and acceleration?

Answer 21

Speed= 0
Drag= 0
Resultant Force= Weight
Acceleration= g

Question 22

There are 3 stages to terminal velocity, what is the 2nd stage (during the flight) relating to: speed, drag, resultant force and acceleration?

Answer 22

Speed is greater than 0
Drag is greater than 0
Resultant Force= mg-drag
Acceleration= mg-drag/m

Question 23

There are 3 stages to terminal velocity, what is the 3rd (At terminal velocity), relating to: speed, drag, resultant force and acceleration?

Answer 23

Speed= constant
Drag= weight
Resultant Force= 0
Acceleration= 0

Question 24

What do we have to assume is negligible for the net force on the skydiver to be zero during terminal velocity?

Answer 24

The upthrust.