Falling Bodies

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1. What is meant by "free fall"?
Free fall means falling ONLY under the influence of the Force of Gravity, i.e. the objects own weight.

This is only possible if there really was no air to create any air friction.
No engines, rockets thrusters, etc. Just gravitational force!

2. What effect does the mass of a body have on free fall acceleration? Answer
The mass of the body does not affect its own free fall acceleration.

This means that a 2kg and a 5kg object will both fall at the same acceleration.

3. What is the vlaue for the gravitational acceleration of any object near the Earth's surface? Answer
a = 9,8m.s-2 down
4. An object is thrown vertically upwards. What is the direction of its velocity and it's acceleration? Answer
velocity direction is UPWARDS.
a = 9,8m.s-2 DOWNWARDS

Even though it is moving upwards, the resultant force (it's own weight) still acts downwards, hence the acceleration is downwards.
acceleration direction = direction of resultant force.

5. A stone is thrown vertically upwards. What is it's velocity and acceleration at the highest point it reaches? Answer
velocity = 0
acceleration = 9.8m.s-2 downwards
(Remember the weight thing! At the highest point, the object still has weight, hence the resultant force is still there. Acceleration is soooo abstract!)
6. When an object is in free fall, which one of the following must be constant?
A. velocity
B. rate at which velocity changes
C. rate at which displacement changes
D. displacement
B. rate at which velocity changes
This is the definition for acceleration! Remember acceleration is constant.
(sneaky buggers!)
7. An object is dropped. What is the direction of it's velocity and acceleration while it falls? Answer
Both are downwards.
8. What is the name for the force with which the Earth attracts a body?
A. acceleration
B. weight
C. gravity
D. mass
B. weight
Weight is the name of that force. Weight is measured in newtons, remember!

Bet you said gravity! That is not a force.
Gravity is a phenomenom phenomomem phenomenon (Whew! Difficult word to spell!) that explains that masses attract each other.
9. A boy throws a stone upwards with a speed of v. It will reach his hand (at the same height) again at a speed :
A. same as v
B. greater than v
C. lesser than v
A. same as v
10. A feather and a coin are dropped simultaneously from the same height in a free fall environment. Which statement is true?
A. The stone will hit the floor first.
B. The feather will hit the floor first.
C. The stone and feather will hit the floor together.
C. The stone and feather will hit the floor together.
There is no friction in free fall, so there is no air to affect the feather.

this question must tickle you!

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