Forces

Question 0

Factors affecting stopping distance

• tiredness, alcohol (thinking distance
• faster speed (thinking distance and braking distance increase)
• poor weather conditions (braking dis)
• poorly maintained vehicles( takes longer to stop as brakes don’t respond very well)

Answer 0

Poor reaction time and high speed both increase thinking distance

Question 1

Forces and braking

• cars travelling at constant velocity have a balanced driving force and resistive force (resultant = 0)
• braking force needed to stop vehicle depends on…
• stopping distance= braking distance( vehicle travels when braking acts) + thinking distance( time for driver to react)

Answer 1

Braking force…. Speed of vehicle when brakes are applied + mass if the vehicle (resultant force= mass x acc)
= grater force needed for greater mass and speed

Question 2

Forces and terminal velocity

Weight=?
Mass=?
Object acted on only by gravity accelerates at ....?
Weight equation?
Object falling through fluid??

Answer 2

Weight(N)= gravitational force acting on it
Mass= quantity of matter (kg)
• accelerates at about 10m/s^2

Question 3

Forces and elasticity

Force applied(N) = spring constant(N/m)x extension (m)

• Is it elastic?
• The extension of the strip of material at any length= present length- original
• the extension of a spring is directly proportional to the force applied to it, as long as limit of proportionality is not exceeded
• What is limit of proportionality?

Answer 3

Is elastic if it returns to original shape after removing force deforming it

Limit of proportionality= the point when it stretches over prediction

Question 4

Spring constant

Answer 4

Equal to the force per unit extension needed to extend the spring, assuming its limit of proportionality is not reached.
Stiffer the spring the greater the spring constant is