Practical 7: Acceleration

What does this practical investigate?

• How varying the force affects the acceleration of an object of constant mass.

• How varying the mass of an object affects the acceleration of an object of constant force.

What is the equipment for this practical?

• Toy car attached to a string.

• String is looped around a pulley

• The other end of the string is attached to a 100g mass.

• Stopclock needed.

What does the weight of the mass provide?

The force acting on the toy car,

What do we draw on the desk?

Chalk lines at equal intervals e.g. every 10cm.

Measure with a meter ruler.

How do we begin this experiment?

• Hold the toy car at the starting point.

• When we are ready we let go of the car.

What happens due to the resultant force in the string?

The car will accelerate along the bench.

What do we need to record?

The time that the car passes each distance marker.

What can happen if the car is moving rapidly?

It will be difficult to record an accurate time.

How do we decrease difficulty in measuring time from the car moving rapidly?

To record the experiment on a mobile phone.

We can then play the video back and record the times accurately.

What do we do once we have done the experiment once?

We repeat the experiment several times, but in each case, we decrease the mass on the end of the string. e.g. 80,40,60,20g

The weight (force) is decreasing each time.

What is the mass that we must keep constant?

• The toy car

• The string

• The mass on the end of the string

  They are all attached so we count them all as the object.

What happens if we take away some of the mass from the end of the string?

We then have to transfer that mass on to the toy car.

By doing that, we keep the overall mass of the object the same.

What does Newton’s second law tell us?

That the acceleration of an object is proportional to the force applied.

The force in this case is the weight of the mass on the end of the string.

We should find that the acceleration of the toy car is proportional to the mass on the other end of the string.

How could we use this equipment to investigate how the varying mass of the object affects the acceleration produced by a constant force?

• Keep the force constant (so same mass)

• Attach the mass to the toy car.

• Record the car as it accelerates along the bench.

• Repeat, increasing the mass on the toy car each time.

What should we find as we increase the mass of the toy car?

The acceleration decreases.