Required Practical Activity 7

Question 1

Method for investigating how varying the mass of an object affects the acceleration produced by a constant force:

Answer 1

1. Set up apparatus as shown in the diagram. Make sure the trolley passes through the light gates before the mass
2. Make sure there are books under the side of the ramp the trolley is being released to compensate for the forces acting against the trolley like air resistance and the friction in the bearings of the wheels of the trolley.
3. Hold the toy car at the starting point
4. When ready let go of the car and catch it once it has passed through both light gates - because of resultant force acting through the string the car will accelerate along the bench
5. Record the acceleration stated on the data loggers in m/s2 to 2 decimal points
6. Repeat experiment three times.
7. Repeat whole experiment again except use lower masses decreasing in intervals of 20g (force (weight) on toy car is decreasing each time).
8. When investigating the effect of changing the force on the acceleration of an object while keeping the mass of the object constant. The object in this experiment is the toy car, string and the mass on the end of the string because they are all attached to each other so they are all counted as the object. So if we decrease the mass on the end of the string we have to move it into the toy car to keep the overall mass of the object the same.
9. Repeat the entire process twice to calculate an average.
10. Plot a graph to show the force against acceleration.

Question 2

What will provide the force acting on the toy car?

Answer 2

the weight of the mass will provide the force acting on the toy car

Question 3

Conclusion for investigating how varying the force affects the acceleration of an object of constant mass:

Answer 3

• Newton’s second law of motion tells 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
• the acceleration of the toy car is proportional to the weight of the mass on the other end of the string

Question 4

Why does the trolley accelerate along the ramp?

Answer 4

• because of resultant force acting through the string the car will accelerate along the bench
• weight is the force that makes the trolley it is the biggest force acting on the trolley causing it accelerate forwards

Question 5

How could the force acting on the trolley be altered?

Answer 5

• the force on the trolley could be altered by changing the mass at the end of the string
• When we are altering the force (weight) on the trolley by changing the mass at the end of the string the the change in mass needs to be added or taken away from the masses in the trolley to make sure the mass of the system doesn’t change
• This is because the force is the independent variable and so the mass of the object has to remain constant and the object in this experiment is the toy car, string and the mass on the end of the string because they are all attached to each other so they are all counted as the object
• So if we decrease the mass on the end of the string we have to move it into the toy car to keep the overall mass of the object the same.

Question 6

How could the mass of the trolley be altered?

Answer 6

• by adding more or taking away masses from the trolley and doing the opposite for the falling masses (mass at the end of the string) to keep the mass of the object the same

Question 7

How could you increase the acceleration of the trolley?

Answer 7

you could increase the acceleration of the trolley by removing masses from the trolly and adding them to the falling masses (masses at end of string) which would increase the force of wight acting on the trolley and therefore increase the acceleration of

Question 8

How does increasing the mass of the trolley affect its acceleration?

Answer 8

• the acceleration of the trolley decreases as the mass of the trolly is increased

Question 9

Why is each measurement repeated three times a mean calculated?

Answer 9

• by finding the mean the effect of random errors is reduced
• to spot anomalies

Question 10

How can you conclude that force and acceleration are directly proportional from data?

Answer 10

• F = ma (m is constant)
• F/a = m which is constant
• as general y/x = constant

Question 11

What is the purpose of the slight tilting of the ramp?

Answer 11

to compensate for the forces acting against the trolley like air resistance and the friction in the bearings of the wheels of the trolley

Question 12

What are the advantages of using light gates connected to a data logger over using stopwatch?

Answer 12

humans have a reaction time that the data logger doesn’t

Question 13

What should you do if you spot an anomalous result when you are still in the process of collecting results?

Answer 13

repeat the result

Question 14

What should you do if you spot an anomalous result after you have gathered all of the results (and recorded them in the table)?

Answer 14

• ignore the anomalies when calculating the mean