RP7: Acceleration

Question 1

What is the aim of this experiment?

Answer 1

• Investigate the effect of varying the force on the acceleration of an object of constant mass.
• Investigate the effect of varying the mass of an object on the acceleration produced by a
  constant force.

Question 2

Outline the first steps of the practical

Answer 2

1. Draw a series of straight lines, each 20 cm apart, perpendicular to the edge of the
   bench.
2. Attach the car to the string at one end, with the other end running across the bench
   pulley.
3. Attach the weight stand to the loose end of string (you may need to tie a knot at that
   end, to hook the stand onto). Hold the weight of the pulley, so it doesn’t pull the car
   but so that the string is fully extended.
4. Release the weight stand (allowing it to fall) and begin the timer. Stop timing when
   the car hits the pulley at the other end of the bench.

Question 3

Describe how you can investigate changing force on a constant mass

Answer 3

A. Add a 10g mass to the weight stack, holding it so it doesn’t pull the car but the string
is fully extended.
B. Release the weights and time the car travelling across the bench.
C. Repeat the experiment by adding 10g weights and recording the time for each.

Question 4

How do you calculate the acceleration?

Answer 4

• acceleration = distance / time^2

Question 5

List some safety precautions

Answer 5

• Don’t stand directly beneath the weight stack, in case any masses become loose and
  fall off the stack - a padded bucket could be placed underneath

Question 6

Suggest a method for marking out 20cm intervals on the desk

Answer 6

• Place pieces of tape every 20cm from the starting point of the trolley
• Use metre rule to measure each interval

Question 7

How would you expect the acceleration of the trolley to change as you add more weights to the end of the spring?

Answer 7

• The more weights that are added, the greater the greater the force that is accelerating the trolley and so the greater acceleration

Question 8

Which of Newton’s laws explains the relationship between force and acceleration?

Answer 8

• Newton’s Second Law
• F = ma

Question 9

Describe how you can investigate changing mass with a constant force

Answer 9

A. Attach a 10g mass on top of the toy car, using either the Blu-Tac or rubber bands.
B. Pull the car back to the starting chalk line.
C. Release the car and time how long it takes for the car to travel across the bench.

Question 10

How can you choose an appropriate quantity of masses to use as the fixed mass for this experiment?

Answer 10

• Carry out a preliminary experiment to find what weight is needed to just accelerate the trolley from rest

Question 11

What would be the consequence of using too large a fixed weight?

Answer 11

• The trolley would accelerate too quickly for the timing at each interval to be accurate

Question 12

How would you expect the acceleration of the trolley to change when you add masses onto the trolley?

Answer 12

• The acceleration will decrease as masses are added to the trolley
• a = F/m

Question 13

Suggest a way that the experiment could be changed to improve the timing of the trolley at each interval

Answer 13

• A video camera could be used to record the experiment and then timings taken from the slowed down video afterwards
• Reduces uncertainty rom human reaction times
• Light gates could be used as well