p4. forces and motion

Question 1

express a displacement

Answer 1

• includes distance = straight line from start to finish
• includes direction of straight line

Question 2

values of speed - walking,running and cycling

Answer 2

walking - 1.5m/s
running - 3m/s
cycling - 6m/s

Question 3

what is velocity?

Answer 3

speed in a given direction

Question 4

how to measure speed on a distance time graph compared to a velocity time graph

Answer 4

• distance time graph = gradient ( rise / run )
• velocity time graph = draw tangent and measure gradient

Question 5

describe lines on a distance time graph
- steep line
- narrow line
- straight line
- curved up line
- backwards line

Answer 5

• steep line = high constant speed ( fast )
• narrow line = low constant speed ( slow )
• straight line = constant speed
• curved up line = acceleration
• backwards line = constant negative speed / velocity ( deceleration )

Question 6

describe lines on a velocity time graph
- steep line
- straight line
- backwards line

Answer 6

• steep line = positive acceleration
• straight line - constant velocity ( zero acceleration)
• backwards line = negative acceleration

Question 7

how to calculate displacement in a velocity time graph

Answer 7

area under graph

Question 8

gravity on earth

Answer 8

9.8m/s

Question 9

what happens when an object falls through a liquid?

Answer 9

• accelerates due to force of gravity
• eventually,resultant force will be 0 and object will move at its normal velocity

Question 10

what is newtons first law?

Answer 10

• object will be at constant velocity ( stationary )
• due to it being a balanced force
• unless acted upon by a resultant force
• uses one object

Question 11

what is newtons second law?

Answer 11

• if mass of an object is constant
• force is then proportional to acceleration
• force = mass x acceleration

Question 12

what is newtons third law?

Answer 12

• every action force from object A onto object B
• has an equal and opposite reaction force from object B back onto object A
• also uses 2 objects

Question 13

RP : effect of varying the force on the acceleration of an object of constant mass

Answer 13

1. position air track on bench with a bench pulley at one end and two light gates above the track.
   - cut interrupt card to known length (10cm) and attach to air track glider
2. connect glider to hanging mass by string,the length of air track passing over bench pulley.
   - ensure that air track is level and card will pass through both gates before mass strikes floor
3. calculate acceleration
4. add 5 x 20 slotted masses to end of string
5. release glider - record weight and acceleration
6. repeat step 4 and 5 two more times and calculate mean value for acceleration
7. repeat steps 4-6 removing one of the slotted masses each time