Youtube:
1. Science with Hazel: https://youtu.be/P8M5MBrQFlg
2.
Mechanics
● Scalar and vector quantities
A vector quantity has magnitude and direction e.g. velocity, force
A scalar quantity has magnitude only e.g. mass, time
● Newton’s 2nd law of motion
Force = mass * acceleration
or, acceleration of a body is directly proportional to unbalanced
force & inversely proportional to mass
or, Rate of change of momentum of a body is directly
proportional to the unbalanced force applied on the body
● Drag force or air resistance increases with speed
● Stopping distance = Thinking distance + Braking distance
Reducing the speed limit reduces thinking distance and braking
distance
Treating roads reduces braking distance only
● Braking distance:
The distance travelled by a car under the braking force
● Explain why the stopping distance of a car increases if the driver
is very tired
The reaction time will increase (1)
Increasing the thinking distance (and so increasing the stopping
distance) (1)
● Explain why it is important that the sled is pulled at a constant
speed.
, If the sled accelerates, the value for the constant of friction would
be wrong
● Terminal velocity (5 marks)
When an object falls through air/liquid, at first the weight of the
object is greater than the opposing force i.e. air resistance. So the
object accelerates downward. As the object falls, air resistance
increases and at any moment of time, the air resistance balances
the weight of the object. The unbalanced force becomes zero.
According to F=ma, force is directly proportional to acceleration.
As F=0, so a=0 and the object falls with constant velocity which is
known as terminal velocity.
A cyclist travels 1500 m from his house to his local shop in 300
seconds.
(a) Calculate the cyclist’s average speed in m/s during his journey.
(2 marks)
(b) On the return home the cyclist accelerates from 2.0 m/s with a
steady acceleration of 2.4 m/s2 . Calculate the time in seconds
that it takes the cyclist to reach a speed of 10 m/s. (3 marks)
A student is measuring gravitational field strength, g, in a classroom
experiment. He takes an object with a mass of 2.0 kg and suspends it
from a newton meter held in his hand. He takes multiple readings of
the object’s weight and calculates an average value of 19.6 N.
, (a) (i) State the equation linking weight, mass and gravitational field
strength. (1 mark)
(ii) Calculate the gravitational field strength in the student’s
classroom and give the unit. (3 marks)
(b) The moon’s gravity is weaker than the Earth’s. State how the
student’s measure of the object’s weight would differ if he
performed the same experiment on the Moon. Explain your
answer. (2 marks)
Work, Power & Energy
● Remember that work done is a scalar quantity. Energy is also a
scalar quantity
● Work done = force * distance
● Energy is often defined as the ability to do work
● Both work and energy have the same unit: Joules (J) or
Newton-metres (Nm)
● Coal is a non-renewable energy resource.
1. Science with Hazel: https://youtu.be/P8M5MBrQFlg
2.
Mechanics
● Scalar and vector quantities
A vector quantity has magnitude and direction e.g. velocity, force
A scalar quantity has magnitude only e.g. mass, time
● Newton’s 2nd law of motion
Force = mass * acceleration
or, acceleration of a body is directly proportional to unbalanced
force & inversely proportional to mass
or, Rate of change of momentum of a body is directly
proportional to the unbalanced force applied on the body
● Drag force or air resistance increases with speed
● Stopping distance = Thinking distance + Braking distance
Reducing the speed limit reduces thinking distance and braking
distance
Treating roads reduces braking distance only
● Braking distance:
The distance travelled by a car under the braking force
● Explain why the stopping distance of a car increases if the driver
is very tired
The reaction time will increase (1)
Increasing the thinking distance (and so increasing the stopping
distance) (1)
● Explain why it is important that the sled is pulled at a constant
speed.
, If the sled accelerates, the value for the constant of friction would
be wrong
● Terminal velocity (5 marks)
When an object falls through air/liquid, at first the weight of the
object is greater than the opposing force i.e. air resistance. So the
object accelerates downward. As the object falls, air resistance
increases and at any moment of time, the air resistance balances
the weight of the object. The unbalanced force becomes zero.
According to F=ma, force is directly proportional to acceleration.
As F=0, so a=0 and the object falls with constant velocity which is
known as terminal velocity.
A cyclist travels 1500 m from his house to his local shop in 300
seconds.
(a) Calculate the cyclist’s average speed in m/s during his journey.
(2 marks)
(b) On the return home the cyclist accelerates from 2.0 m/s with a
steady acceleration of 2.4 m/s2 . Calculate the time in seconds
that it takes the cyclist to reach a speed of 10 m/s. (3 marks)
A student is measuring gravitational field strength, g, in a classroom
experiment. He takes an object with a mass of 2.0 kg and suspends it
from a newton meter held in his hand. He takes multiple readings of
the object’s weight and calculates an average value of 19.6 N.
, (a) (i) State the equation linking weight, mass and gravitational field
strength. (1 mark)
(ii) Calculate the gravitational field strength in the student’s
classroom and give the unit. (3 marks)
(b) The moon’s gravity is weaker than the Earth’s. State how the
student’s measure of the object’s weight would differ if he
performed the same experiment on the Moon. Explain your
answer. (2 marks)
Work, Power & Energy
● Remember that work done is a scalar quantity. Energy is also a
scalar quantity
● Work done = force * distance
● Energy is often defined as the ability to do work
● Both work and energy have the same unit: Joules (J) or
Newton-metres (Nm)
● Coal is a non-renewable energy resource.
