Forces and motion

Question 1

Describe an experiment to investigate the motion of everyday objects

Answer 1

1. Measure out a height of 1.0 m using the tape measure or metre ruler
2. Drop the object (paper cone or tennis ball) from this height, which is the distance travelled by the object
3. Use the stop clock to measure how long the object takes to travel this distance
4. Record the distance travelled and time taken
5. Repeat steps 2-3 three times, calculating an average time taken for the object to fall a certain distance
6. Repeat steps 1-4 for heights of 1.2 m, 1.4 m, 1.6 m, and 1.8 m

Question 2

What errors should you keep in mind for the tennis ball/dt experiment?

Answer 2

1. measurements on the tape measure or metre rule are taken at eye level to avoid parallax error
2. using an electronic sensor, such as light gates, to obtain highly accurate measurements of time
3. done in a space with no draught or breeze, as this could affect the motion of the falling object
4. ball bearing and an electronic data logger, like a trap door, is a good way to remove the error due to human reaction time for this experiment

Question 3

define acceleration

Answer 3

rate of change of velocit

Question 4

what does a velocity time graph show

Answer 4

how the velocity of a moving object varies with time

Question 5

what other info does v time graph show

Answer 5

If the object is moving with a constant acceleration/deceleration

The magnitude of the acceleration/deceleration

Question 6

what does area under a VT line represent

Answer 6

displacement

Question 7

what are scalars

Answer 7

quantities that have only a magnitude

Question 8

what are vectors

Answer 8

both a magnitude and a direction

Question 9

what’s friction

Answer 9

The force which opposes the motion of an object

Question 10

what’s weight

Answer 10

The force acting on an object due to gravitational attraction

Question 11

what does weight do?

Answer 11

1. Objects stay firmly on the ground

2.Objects will always fall to the ground

3. Satellites are kept in orbit

Question 12

define ‘stopping distance’

Answer 12

The total distance travelled during the time it takes for a car to stop in response to some emergency

Question 13

whats the eq for stopping distance

Answer 13

Stopping distance = Thinking distance + Braking distance

Question 14

what factors affect stopping distance?

Answer 14

VEHICLE SPEED - the greater the speed, the greater the vehicle’s braking distance will be (because the brakes will need to do more work to bring the vehicle to a stop)

VEHICLE MASS - a heavy vehicle, such as a lorry, takes longer to stop

ROAD CONDITIONS - wet or icy roads make it harder to decelerate

DRIVER REACTION TIME - a driver’s thinking distance depends on their reaction time. Being tired, or intoxicated (i.e. alcohol, or drugs) can increase reaction time

Question 15

What 2 forces do falling objects experience?

Answer 15

Weight (due to gravity)
Air resistance (due to friction)

Question 16

describe terminal velocity

Answer 16

• UPWARDS AIR RESISTANCE is very small because the skydiver isn’t falling very quickly
• there are UNBALANCED FORCES on the skydiver initially
• As skydiver speeds up, air resistance increases, eventually growing large enough to BALANCE the downwards weight force
• Once air resistance equals weight, the forces are BALANCED
• no longer any RESULTANT force
• skydiver’s acceleration is zero - they now travel at a CONSTANT SPEED
• This speed is called their TERMINAL VELOCITY

Question 17

Core Practical 2: Investigating Force & Extension
(can be used for both spring and rubber band)

Answer 17

1. Set up APPARATUS
2. Align the marker to a value on the ruler, record this INITIAL LENGTH of the spring
3. Add the 100 g MASS hanger onto the spring
4. RECORD the mass (in kg) and position (in cm) from the ruler now that the spring has extended
5. Add another 100 g to the mass hanger
6. RECORD the new mass and position from the ruler now that the spring has extended further
7. REPEAT this process until all masses have been added
8. REMOVE the masses and REPEAT the entire process again, until it has been carried out a total of three times, and an average length is calculated

Question 18

Investigating force-extension apparatus for a metal (e.g. copper) wire

Answer 18

1. Set up the apparatus so the WIRE IS TAUT
2. Measure the ORIGINAL LENGTH of the wire using a metre ruler and mark a REFERENCE POINT with tape near the beginning of the scale
3. Record the INITIAL reading on the ruler of the reference point
4. Add a 100 g MASS onto the mass hanger
5. Read and record the NEW READING of the tape marker from the meter ruler now that the metal wire has extended
6. REPEAT this process until all masses have been added
7. Remove the masses and repeat the entire process again, until it has been carried out a total of three times, and an average length (for each mass attached) is calculated

Question 19

WHAT DOES HOOKE’S LAW STATE

Answer 19

The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality

Question 20

when does elastic deformation occur

Answer 20

When objects return to their original shape when the stretching force is removed

Question 21

when does inelastic deformation occur

Answer 21

When objects remain stretched and do not return completely to their original shape even when the stretching force is removed