Forces in Action
Energy and Efficiency
Speed and Motion
Levers and Moments
Simple Machines
100
Name 2 forces that act on a falling object.
Gravity and air resistance
100
Name 3 types of energy stores
Chemical, thermal, kinetic, gravitational potential, nuclear, elastic potential, electromagnetic, electrostatic
100
What is the formula for calculating speed?
Distance/time
100
What is the name for a turning point?
What is meant by the term 'load'?
Turning point: pivot
Load = resistance
100
Name 3 kinds of simple machines
Lever, pulley, ramp, wheel, screw
200
A car's forces are balanced. What does this tell you about its movement?
The car is either staying still OR moving at a constant speed.
200
Name 3 ways in which energy can be transferred
Heating, sound, radiation, electrical, light, forces
200
What are the 3 different units that can be used for speed?
km/h, m/s, mph
200
How do you calculate moment?
Moment (Nm) = Force(N) x distance from pivot
200
What does a simple machine do to make work easier?
It changes the direction or size of the force
(force multiplier or distance multiplier)
300
Draw a diagram that demonstrates the forces on a car that is slowing down. (no need to label)
300
This image shows energy efficiency of a light bulb. If 100J is put in and 80J is useful, how much is wasted, and what type of energy is wasted?
20J Heat energy (thermal)
300
A car travelling at 50km/h overtakes a car travelling at 30km/h. What is the relative speed of the faster car compared to the slower car?
50-30 = 20km/h
300
Are the anticlockwise and clockwise moments balanced? Show your work.
Anti: 300 x 2 = 600 N m
Clockwise: 400 x 1.5 = 600 N m
Yes!
300
What is the formula for work?
Work = Force x Distance
400
What is the resultant force of this object?
45N right (or -->). Both arrows pointing right.
400
What is the equation for calculating energy efficiency as a percentage?
(Useful energy/total energy input) x 100%
400
What is the gradient between 5 and 15 seconds?
75-50/15-5 = 15/10 = 1.5 m/s
400
How does the length of a lever affect the effort needed?
longer lever = less effort required
400
This image shows 1 pulley vs 2 pulleys. If the object being pulled is 200N, how much force will be required in image X vs image Y?
Image X = 200N
Image Y = 100N
Pulleys are force multipliers!
500
Why do vehicles have a top speed?
Forward force is as large as the friction and resistance
500
80J of energy is transferred to a light bulb. 20J gets transferred by light. Calculate its efficiency percentage.
20/80 x 100 = 25%
500
A cyclist travels 600m in 50s. They stop for 30s, then travel another 400m in 20s. What is their average speed?
Total distance/total time = 1000/100 = 10 m/s
500
A seesaw has a pivot in the middle. A 500N person sits 2m from the pivot. Where must a 250N person sit in order to balance it?
500 x 2 = 250x
1000= 250x
x = 4m from the pivot
500
Calculate the work done to move this box up the ramp. Include units.
work = 500N x 4m
Work = 2000J