Physics - Forces 2

REQUIRED PRACTICAL 6 - What is the set-up and method for the required practical on investigating how mass and force affect acceleration?

Draw a line on a ramp.
Place the trolley on the ramp, with a turretted card, to do a double interrupt with one light gate (or use a simple card, and two light gates)
Have a light gate positioned so the card goes through it as the trolley goes down. A pulley system should be at the bottom of the ramp, and , below it, a bucket of sand (catching the weights and preventing any potential hazard)

Add a weight to the trolley (mass) or pulley hook (force). Release the trolley, and note the value on the data logger. Repeat this 3 times and calculate an average.
Add a weight and repeat
Draw a graph from your results

Why would you tilt the ramp?

To overcome the force of friction

Why does the piece of card on the trolley have a gap in the middle?

So that is interrupts the signal on the light gate twice, allowing the data logger to measure acceleration

What should you do to always make sure you let go of the trolley at the same place?

Mark a starting line on the table for the trolley

After letting go of the trolley and letting it run through the light gate, what will the data logger (which is connected to the light gate) tell you?

The acceleration

What can you do to investigate the effect of the mass alone?

You can add masses to the trolley one at a time to increase the mass of the system, but not add masses to the hook as that would change the force.

What can you do to investigate the effect of the force alone?

You can keep the total mass of the system the same, but change the mass on the hook. To do this, start with all the masses loaded onto the trolley, and transfer the masses to the hook one at a time, to increase the accelerating force.

Force acceleration mass equation

F=MA

Force is BLANK proportional to acceleration so the graph is BLANK

Directly; a straight line through the origin

Force is BLANK proportional to mass so the graph is BLANK

Inversely; a line with is steep at first, come down, then is almost horizontal going right |_

What is Newton's second law

The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.

What is inertial mass

How difficult it is to change the velocity of an object
The resistance an object has to a change in its velocity

Inertial mass equation

force/acceleration

Momentum law

Momentum is conserved in any explosion or collision

Momentum equation

Momentum (kmm/s) = mass (kg) x velocity (m/s)
p=mv

Momentum is a scalar/vector quantity

Vector

Velocity is in/directly proportional to momentum

directly

Mass is in/directly proportional to momentum

directly

Force - momentum - time equation
What does this mean then?

Force = change in momentum/time
Increasing the time of a collision decreases the force

How does a crumple zone keep you safe in a collision

The front and back of the car has steel bars which crumple in a collision, increasing the collision time and decreasing the force

What do airbags, bicycle helmets and gym crash mats have in common

They all use padding which compresses when a force is applied, increasing the time of the collision, and, therefore, decreasing the impact on the person, hopefully preventing death or serious injury

What do seatbelts do in a crash

They stretch, increasing the time of the collision and therefore decreasing the force. They also stop you from hitting your head on the dashboard or windscreen, so, though you may be bruised, you will be less likely to sustain a serious injury

What impacts stopping distance

The driver
Reaction time
Distractions
Tiredness
Alcohol
The vehicle
Condition of the brakes
Track on the wheels
Mass
speed
The road
Grit
Ice, rain, etc