PAG 01.3 Investigating Initial Speed And Stopping Distance Flashcards
What is an interrupt card?
A length of card of a known length. It is attached to a moving object at the height of the light gates, and cuts the light beam as it passes through them
How can the initial velocity be calculated from the data recorded by the light gate?
The light gate will record the time taken for the interrupt card to pass through. The length of the interrupt card can be divided by the time to obtain the velocity
Where should the light gate be set up in this experiment and what does it record?
The light gate should be positioned at the start of the metre ruler, so that it can measure the initial speed of the block
When pushing the block, why must you release it before it passes through the light gate?
If you are still applying a force as it passes through the light gate, it will cause the block to accelerate
This will result in an inaccurate initial speed measurement
Why does the block eventually come to a stop?
Due to the frictional force acting between the block and the surface
Describe the energy transfer that takes place in this experiment
The kinetic energy of the block is converted into thermal energy as work if done against friction
Write an energy balance equation for this experiment
1/2mv^2=Fd
Kinetic energy= work done against friction
What assumption about friction do we make in this experiment
We assume the frictional force is constant across the distance travelled
Fair assumption due to relatively low speeds
What is the relationship between stopping distance and initial velocity?
v^2 (proportional sign) d
Predict how the stopping distance of the block will change when it’s initial velocity is doubled
v^2 proportional to d
This relationship suggests that when the initial velocity is doubled, the stopping distance will quadruple
Why is it important that the material of the block and the surface along which it slides is the same throughout the experiment?
The two surfaces must remain the same so that the frictional force doesn’t change throughout the experiment
What graph should be plotted with the data obtained from this experiment?
A graph of stopping distance against velocity squared should be plotted. Since the two quantities are directly proportional, this should form a straight lines through the origin
Why can repeat readings not be taken when carrying out this experiment?
It will be difficult to achieve the same exact initial velocity each time
Why may it be advantageous to plot the data points as you carry out the experiment?
By plotting as you carry out the experiment, you can quickly spot an anomalous result, and take another recording around the same velocity to replace it
