Motion and Force Flashcards
What is Newton’s first law of motion?
Objects will either stay at rest or travel at a constant velocity unless acted upon by a resultant force.
What is Newton’s second law? What is the equation it is shown by?
Force is proportional to the mass an acceleration of the object
F=mxa
How can F = ma be applied when two forces on an object are in opposite directions?
Resultant force = F1-F2 = ma
What is thinking distance?
equation?
distance travelled by a vehicle in the time it takes the driver to react.
S1 = speed x reaction time = vt0 (t0 = reaction time)
What is braking distance?
equation?
Distance
travelled by a car in the time it takes to stop safely once the brakes have been applied.
S2 = v^2 / 2a
(because v^2 = 2as)
v = velocity a = deceleration s = distance
What is stopping distance?
It is the total distance needed to stop, this is thinking distance + braking distance. this means that the equation for this is,
S1 + S2 = vt0 = v^2/2a
(v = speed before brakes were applied)
Safety features of cars?
what is the main thing these features provide?
Vehicle bumpers crumple zones seat belts collapsible steering wheel airbags all of these features are designed to increase the impact time and so in turn reduce the impact force.
What happens to the forces on a sky diver when they jump out of the plane?
They initially start accelerating as their weight is acting downwards. As they accelerate the drag force due to air resistance increases and slows the downwards acceleration. They will eventually get to a point when their weight is the same as the drag force. At this point the skydiver has reached its terminal velocity.
For an object on a slope of angle theta and mass m there is a component of the force that acts down the slope. What is this component?
From this we can find out what the acceleration of the object would be down the slope, how would we do this?
F=mg sin theta
(where the weight is mass x gravity)
F = ma = mg sin theta a = g sin theta
