Weight And Terminal Velocity

Weight and terminal velocityWeight and terminal velocity

objectivesobjectives

• calculate an object’s weight

• describe what terminal velocity is and how it comes about

• draw and interpret velocity–time graphs for objects that reach terminal velocity

starterstarter

what is the odd one out?

explain why.

kg g N lbs mg st oz

Gravity and weightGravity and weight

weight (N) = mass (kg) x gravity (N/kg)

• on Earth, there is 10N force on each 1kg mass

what is your mass?what is your mass?

what is your weight?what is your weight?

2 minute quick questions

speed and drag

• http://www.bbc.co.uk/learningzone/clips/why-does-a-human-have-a-different-terminal-velocity-to-a-mouse/8751.html

Terminal Velocity

P2.6d Terminal velocity–time graphs 1 For each of the six stages listed below

i write down what the resultant force will be, and

ii what will happen to the velocity of the skydiver.

a Start: leaps from plane: velocity = 0 m/s; weight = 750 N; air resistance = 0 N.

b After 1 second: falling slowly; weight = 750 N; air resistance = 250 N.

c After 4 seconds: falling fast; weight = 750 N; air resistance = 450 N.

d After 10 seconds: terminal velocity of 54 m/s; weight = 750 N; air resistance = 750 N.

e After 12 seconds: parachute opens; air resistance = 1500 N; weight = 750 N.

f After 17 seconds: weight = 750 N; air resistance = 750 N; new terminal velocity of 3 m/s.

2 Use your answers to parts a to f to help you sketch a velocity–time graph for the movement of the skydiver.

• exam q

to finish with to finish with

• The _______________ of an object can be calculated using the equation: W = m x g. On Earth, this means the weight is 10 times the mass, as the Earth’s gravitational field _______________ is 10 N/kg. The faster a body moves through a fluid, the _______________ the frictional force on the object. A body falling through a fluid will _______________ at first because of its weight. This will increase the friction, so the resultant force will _______________. It will continue to accelerate until it reaches a terminal velocity when the weight is balanced by the _______________.

• friction greater reduce strength weight accelerate