Units
The unit of mass
kilograms (kg)
Scalar - has only magnitude
Vector - has magnitdue and direction
A horizontal line on a distance-time graph represents....
no movement
A boat's engine provides a force of 50N to push it forwards. It feels resistive forces of 20N. What is the resultant force on the boat?
50 - 20 = 30N forwards.
What is Newton's Second Law?
F = ma
Resultant force on a body = mass of body multiplied by the acceleration of the body.
The unit of weight
Newtons (N)
Give an example of 1 contact and 1 non-contact force
Contact: Friction, Air Resistance, Reaction Force, Tension
Non-Contact: Gravity, Electrostatic, Magnetic
A straight diagonal line on a distance-time graph represents...
Calculate the speed of a car which travels 40m in 10s.
Speed = distance / time = 40 / 10 = 4m/s
What is Hooke's Law? What is k and what is it measured in?
The extension of a spring is directly proportional to the force applied to it.
F = ke -> k = spring constant, measured in N/m
metres per second (m/s)
What is the difference between mass and weight?
Mass: the amount of matter within a body, measured in kg.
Weight: the force felt by a body due to the gravity of Earth, measured in N.
A horizontal line on a velocity time graph represents....
constant speed
A car is stopped at a red light. When the light turns green, the driver accelerates to 50m/s in 10 seconds. What is the acceleration of the car?
Acceleration = change in velocity / time
= (50 - 0) / 10 = 50 / 10 = 5m/s2
Sketch the force-extension curve of a spring that passes its elastic limit.
Define the elastic limit
The units of acceleration
metres per second2 (m/s2)
Finish Newton's 1st Law:
If the resultant force on an object is zero, it will...
remain in motion if already in motion, or remain stationary.
A straight diagonal line on a velocity time graph represents...
Constant acceleration
A truck of mass 500kg is travelling at 40m/s. It collides with a stationary car of mass 300kg. The car moves forwards at 10m/s. What is the velocity of the car after the collision?
Momentum = mass x velocity
total momentum before = total momentum after
Before: (500x40) + (300x0) = 20000kgm/s
After: (500xv) +(300x10) = 500v + 3000
20000 = 500v + 3000
17000 = 500v
v = 17000/500 = 34m/s forwards
Foam on the floor to protect feet if trolley falls off ramp
Masses fixed to the trolley to prevent them falling off and injuring someone.
The units of momentum
kilogram metres per second (kgm/s)
Find the horizontal and vertical components of a 10N force acting at 25 degrees to the ground. Give your answers to 2dp.
Horizontal = 10cos(25) = 9.06 N
Vertical = 10sin(25) = 4.23 N
the object moving backwards.
A car decelerates from 40m/s to 20m/s in 5 seconds. How far does it travel in this time?
a = (v-u)/t = (20 - 40)/5 = -20/5 = -4m/s2
v2 - u2 = 2as so s = (v2 - u2)/2a
s = (202 - 402)/(2 x -4) = -1200/-8 = 150m.
Give 1 way that errors can occur when trying to find the spring constant of a spring.
Ruler not parallel to spring - extension measured wrong
Ruler not aligned with top of spring - initial length of spring measured wrong.
Spring not stationary before measurement of length taken - extension measured wrong.