section 1 forces and motion a) units b) movement and position

Question 1

1.1 use the following units: kilogram (kg), metre (m), metre/second (m/s), metre/second2 (m/s2), newton (N), second (s), newton per kilogram (N/kg), kilogram metre/second (kg m/s).

Answer 1

Unit of mass=Kilogram (kg)
Unit of distance=Metre (m)
Unit of speed or velocity= Metre per second (m/s)
Unit of acceleration= metre per second2 (m/s2)
Unit of Force= Newton(N)
Unit of Time= Second(s)
Unit of gravitional acceleration= Newton per kilogram(N/kg)
Unit of Momentum= kilogram metre per second (kg m/s)

Question 2

1.2 plot and interpret distance- time graphs

Answer 2

Distance time graph
http://www.shawonnotes.com/IGCSE_Physics/physics_images/distance-time-graph.png

A distance-time graph represents the speed or velocity of any object. In this graph the object is moving at 1 m per second. It is in a constant speed. In a distance-time graph, distance should go to the Y-axis while time should go over the X-axis.

Speed= gradient=distance/time = 3m/3s= 1m/s

Few points that should be noted

1) In a displacement – time graph or distance- time graph, the average velocity is found by the ratio (△s)/(△t) where △s = change in displacement/distance and △t=time interval
2) A positive gradient of the displacement-time graph indicates that the car is moving in the same direction as the displacement.
3) A negative gradient of the displacement-time graph indicates that the car is moving in the opposite direction to the displacement.
4) A zero gradient of the displacement-time curve shows that the car is stationery.

For diagrams of zero displacement, constant displacement, not moving, deceleration and acceleration
http://www.shawonnotes.com/index/forces_and_motion/0-9

Question 3

1.3 know and use the relationship between average speed, distance moved and time:

Answer 3

average speed = distance move/ time taken

Question 4

1.4 describe experiments to investigate the motion of everyday objects such as toy cars or tennis balls

Answer 4

http://www.shawonnotes.com/IGCSE_Physics/physics_images/speed-lightgate.jpg

1) Attach a card of measured length centrally to the top of the toy car.
2) Air track ensures a frictionless way for the toy car.
3) A gentle push can move the toy car at a steady speed.
4) Arrange for the card to block a light gates beam as it passes through it.
5) Electronic timer measures how long the card takes to pass through the beam.
6) Now calculate the toy car’s average velocity as it passes the light gate by: v = length of the card / interruption time

Question 5

1.5 know and use the relationship between acceleration, velocity and time:

Answer 5

acceleration = (final velocity - initial velocity)/ time taken

a= (v-u)/t

Question 6

1.6 plot and interpret velocity-time graphs

Answer 6

Velocity-time graphs represent the acceleration of any object. Velocity(m/s) is in the Y-axis while Time is the X-axis.

http://www.shawonnotes.com/IGCSE_Physics/physics_images/velocity-time-graph.png

Question 7

1.7 determine acceleration from the gradient of a velocity-time graph

Answer 7

http://www.shawonnotes.com/IGCSE_Physics/physics_images/gradient-acceleration.jpg

Acceleration = gradient
= (y2 - y1)/(x2 - x1 )
= (200-0)/(50-0)
= 4 ms2

Question 8

1.8 determine the distance travelled from the area between a velocity-time graph and the time axis.

Answer 8

http://www.shawonnotes.com/IGCSE_Physics/physics_images/areaunderthegraph.jpg

Distance travelled = area under the graph 
= 1/2(a+b)h
= 1/2(100 + 40) x 150
= 1/2 x 140 x 150
= 10500 m