Year 8 Bonus Review
The South pole of a magnet will attract the _______ pole of another magnet
North
What is Newton's second law?
Force = Mass x Acceleration
(The greater the mass, the more force needed to accelerate)
Projectile motion is the motion of an object on a _____________ path due to the effects of gravity.
Curved (or parabolic).
The moon orbiting the earth is what type of centripetal force?
A. Gravity
B. Tension
C. Friction
D. Normal
A. Gravity
Why do we see fireworks before we hear them?
Light travels faster than sound!
If the amount of force is the same, a greater mass means a ______________ acceleration.
A. Faster
B. Slower
B. Slower acceleration!
Does air resistance increase of decrease the trajectory (path) of an object?
Decreases
List two reasons why skiing down a very steep hill cannot be considered free fall.
Other forces besides gravity:
-Air resistance
-Friction (skiis and the snow)
A racecar driving around a circular track is what type of centripetal force?
A. Gravity
B. Tension
C. Friction
D. Normal
Friction
What is the equation we use to measure pressure?
Pressure = Force/Area
Which has more inertia:
A. A pencil
B. Your backpack
C. A pro football player
D. A desk
C. A pro football player (the greater the mass, the greater the inertia).
Interia=object remains unchanged, much harder to change the motion of a football player than a pencil.
Projectile motion is caused by what TWO directions of velocity?
Horizontal (forward velocity) and vertical (downwards velocity due to gravity)
Explain how an open parachute increases air resistance for a falling skydvier.
The parachute increases the surface area, because a higher surface area = more air resistance
If I am swinging a ball on a string, what is the direction of the centripetal force?
Towards the center.
Why does it hurt more to stand on one needle than a bed of needles?
Because the needle has a smaller surface area, and therefore more pressure
Use two of Newton's laws to explain what happens when you hit a padel ball with a racket.
Newton's Third Law: You apply a certain force to the ball, and that same force is applied back into the racket.
Why does a rock falling straight down hit the ground at the same time as one that is launched?
The rocks have the same vertical velocity (change in speed and direction). There is no change in the horizontal velocity of the launched rock.
As an astronaut travels farther from earth, what happens to her weight?
A. Her weight increases because gravity increases
B. Her weight decreases because gravity decreases
C. Her weight stays the same even though gravity changes
B. Her weight decreases because gravity decreases. Remember that WEIGHT has to do with gravity, while mass is just how much space something takes up. The weaker the gravitational pull, the less you will "weigh."
A Rollercoaster going around a loop is what 2 centripetal forces?
A. Gravity
B. Tension
C. Friction
D. Normal
Gravity and Normal
Explain why a firetruck seems louder when it is passing you, than when you hear it from a distance.
The firetruck seems louder because the sound waves are entering your ear at a greater frequency (rate) as you get closer. When it gets farther, less sound waves are reaching your ear. This is known as the Doppler Effect.
Explain how Newton's second law applies to riding a bicycle.
With the same mass, the more force you apply to the pedals, the more you will accelerate (F = M x A)
What is the name for the arrows we use to measure force?
Vector
The bowling ball and feather will fall much slower on the moon, since the acceleration due to gravity is slower.
A little girl swinging her cat by its tail is which centripetal fore?
A. Gravity
B. Tension
C. Friction
D. Normal
B. Tension