Forces
Contact force examples: friction, normal, muscular, elastic
Non-contact force examples: gravity, magnetic
Acceleration
How many Laws of Motion did Isaac Newton create?
3
The amount of work done over a period of time is called:
Power
10 m/s
What is the Normal Force?
Force that opposes gravity when an object is on a flat surface or a similar answer.
What are the units for acceleration?
N/kg or m/s2
What is the formula for Newton's 2nd Law?
F = ma
Give three examples of simple machines.
Pulley, lever, screw, wheel and axle, inclined plane, or wedge.
It takes 150 N of force to accelerate an object at 5m/s2. What is the mass of the object?
F = ma, so m = F/a = 150N / 5m/s2
m = 30 kg
Give one example of when forces are balanced and one example of when forces are unbalanced.
Forces balanced when acceleration is zero (person sitting still).
Forces unbalanced when acceleration is not zero (car accelerating).
A football flying through the air is an example of:
Projectile Motion
A 10kg object accelerates at 5 m/s/s. How much force is required?
F = 10kg*5m/s/s = 50 N
Mr. Chari pushes his car with a force (kraft) of 400N but it still does not move. How much work (arbete) is done?
No work is done
A capybara has a mass of 40kg. If it flies to the moon (g=2 N/kg), what is its weight?
80 N
What is Centripetal Force? Which direction does it act?
Any force that makes an object move on a circular path. It acts towards the centre of the circle.
What is the acceleration of an object in free fall on Earth?
10 m/s
Explain Newton's First Law, the Law of Inertia.
Objects continue doing what they are doing unless acted upon by a new or outside force.
Which scenario requires more work: Walking up a set of stairs or running up a set of stairs?
They both require the same amount of work. W=Fd, Force and distance do not change and time has no impact on Work.
It takes 100 J to walk 10m in 5s. Calculate the Power.
20 Watts
Describe the difference between mass and weight.
Mass, measured in kg, is the amount of matter in something. Weight, measured in N, is the force of gravity acting on something.
What would happen if you were spinning really fast and the centripetal force (centripetalkraft) suddenly stopped?
Explain Newton's Third Law.
For every action (force) there is an equal and opposite reaction (counter-force).
What is the trade-off when using an inclined plane?
Work is done over a greater distance so less force is required. This makes the work feel easier.
I lift a box full of books from the floor to a shelf 2 meters tall. The book box has a mass of 15kg. How much Work am I doing?
Answer is 300J.The mass of 15kg weighs 150N (Fgravity = mg).
W = Fd = 150N*2m = 300 J