Waves
Explain what a medium of a mechanical wave is and give an examples
A medium is the substance in which a wave moves through. Example: air, water.
Name 3 vector quantities
position, displacement, velocity, acceleration, force, momentum
What is Newton's 1st law?
An object will maintain a constant velocity unless an unbalanced, external force acts on it.
What is the equation of momentum and what are its SI units?
p = mv
kgms-1
What is the equation for finding the period of a wave?
T=1/f
a girl swims ten lengths of a 25m pool. Which one or more of the following statements correctly describes her distance travelled and displacement?
A: her distance travelled is 0
B: Her displacement is 0
C: Her distance travelled is 250 m
D: Her displacement travelled is 250 m
B & C
Calculate the net force causing a 5.50kg mass to accelerate at 3.75ms-2 west.
= 20.6 N west
Explain conservation of momentum
momentum will be conserved in any interaction or collision between objects. This means that the total sum of momentum in any system before a collision will be equal to the total sum f moment in the system after the collision.
What is the equation for finding the velocity of a wave?
velocity = frequency (Hz) x wavelength (m)
v = f • λ
How can you figure out the displacement of an object in a velocity-time graph?
given by the area under a velocity-time graph.
Identify the action/reaction pair of a table-tennis bat in contact with a table-tennis ball
Force on ball by bat (action force)
Force on bat by ball (reaction force)
Calculate the momentum of a 965 kg car moving east along a highway at 90.0 kmh-1
=965 x 25
= 241 00 kgms-1 East
In an experiment to determine the speed of sound in water, a 450 Hz sound was found to produce 3.17 m waves. Find the velocity of the sound in the water.
v = 3.17 x 450
= 1430 ms-1
A marble rolling at 1.20 ms-1 starts accelerating down a hill at 0.560 ms-1. How far down the hill does the marble roll in 3.60 s?
s = ut+0.5at2
= 7.95m
Would your weight be greater on Earth or on the moon? Explain your answer
It would be greater on Earth. The gravitation field is much stronger on Earth compared to the moon. Therefore the force due to gravity will be larger, resulting in a larger weight force.
In cricket, the wicket keeper wears gloves that contain a thin layer of padding. Explain, using physic principles, how the glove helps reduce the damage to the keeper's hand when catching a fast moving, hard cricket ball.
i = ft
the padding in the gloves will increase the time over which the impact occurs, therefore the force applied on the hands will decrease. Less force results in less damage to the hands.
A surfer is not having much luck on her early morning surf. She passes the time waiting for the swell to pick up by estimating that the period of the small waves is 5.80 s and that as she floats on the crest of one wave, the next crest is 15.0 m away. Find velocity and frequency of the ocean waves.
Find frequency: f= 1/5.80 = 0.172Hz
Find velocity:
v = 15 x 0.172
=2.59 m/s-1
A car is approaching traffic lights at 60.0 kmh-1 . The driver observes the traffic light turn red and manages to stop the car in 5.60 s. Find the acceleration of the car.
The car decelerates at 2.98 ms-2
A 600 g ball rolling at 2.30 ms-1 comes to rest over 4.20 s. Calculate the average frictional force acting on the ball.
Find acc.
f = ma
= - 0.329 N
The driver of a 1250 kg car is heading north towards a school and slows from 60.0 kmh-1 to 40.0 kmh-1 as he enters the school zone. Find the change in momentum of the car
= - 6950 kgms-1