Author: molly stones

Why is the orbit time for Mercury shorter than Saturn’s? Use at least one equation in your answer.
time=speed/distance
Mercury travels faster than Jupiter as the force of gravity it experiences from the Sun is greater as it is closer. Also, the distance mercury travels is shorter.

How does a seatbelt prevent injury? Use at least one equation in your answer.
Force=change in momentum/time
Seatbelts increase the time it takes for the change in momentum to occur so the force experienced by the person is reduced. Less force means injury is much less likely.

State one piece of evidence for light being a wave.
The interference of light can only be explained if light is a wave.

How is the ionosphere used in communication?
Radio waves can be bounced off the ionosphere to take signals across the world.

Why does a gun recoil?
Every action has an equal and opposite reaction. The gun recoils in reaction to the bullet leaving the barrel.

What is the critical angle?
The angle of incidence in the more dense medium that produces an angle of refraction of 90* in the less dense medium. If it is exceeded total internal reflection occurs.

Complete the diagram to show what focal length is. Include the following labels: convex lens, principal axis, focal point.

Ball A and B collide. Ball A is initially travelling 5m/s with ball B stationary. After they collide Ball A is stationary. Ball A is 5kg and ball B is 2kg. What is the velocity of ball B after the collision? Show the equations you use.
momentum=mass x velocity
Initial momentum= (5 x 5) + (2 x 0)=25kgm/s
Final momentum=25kgm/s= (5 x 0) + (2 x v) = 2v
25/2 = 12.5m/s

Draw a diagram to show the motion of a tennis ball that had just been bounced off the floor.

A car starts at 10m/s and accelerates to 25m/s over 10 seconds. What was it’s acceleration?
v=u + at
a= (v-u)/t
a= (25-10)/10
a= 15/10
Answer 1.5 m/s2

Draw the resultant vector if a plane flies 20km due North and 15km due East.
202+152=625
sq root 625=25 25km

What do the following things represent in equations? What are their units?
s = distance travelled(m) u = initial velocity (m/s) v = final velocity (m/s) a = acceleration (m/s2) t = time (s)
sin i= sine of angle of incidence
sin r= sine of angle of refraction
n= refractive index
c = critical angle

At point A two waves interfere. Point A is 9cm away from source 1 and 15cm away from source 2. The wavelength is 3cm. Will the interference be constructive or destructive? Why?
The path difference is 6cm. 6/3=2. Therefore the path difference is a whole number of wavelengths, so the interference will be constructive.

Name 2 scalar quantities.
Mass, Speed,
Name 2 vector quantities.
Weight, force, acceleration, velocity,