Chapter 1 - Motion Flashcards Preview

Physics Stage 3AB > Chapter 1 - Motion > Flashcards

Flashcards in Chapter 1 - Motion Deck (30):
0

If you want to throw a ball as far as possible the best angle to throw it is 45 degrees above the horizontal. Explain why this gives the maximum range.

To achieve the maximum range ie. the longest throw the time of flight (as as horizontal velocity) must be a maximum. The higher the projectile goes the longer the time of flight so it must be thrown so that there is some vertical velocity. The reality is that there must be a compromise between time of flight and horizontal velocity (best theoretical angle is 45 degrees), as well as angle at which the maximum force is achieved by the thrower.

1

What is Centripetal Force?

It is the horizontal component which is unbalanced and it acts towards the centre of the circular path.

2

How does Safety Factor work?

When calculating the force to be withstood by the attachments holding a horse onto a carousel, or restraints on any other ride, safety standards usually require that the actual force that can be withstood must be several times larger than the actual force.

A safety factor of 10 means 10 times the expected force must be able to be withstood.

3

What affects the length of a roller coaster ride?

The height in which the cart is hauled at the start, and the friction between the car and the track.

4

What does the Gravitation Potential Energy Equation states?

It states that the work done to raise an object in a gravitational field is:

Ep=mgh

5

If air resistance is ignored, what forces act upon the projectile?

The only force acting on a projectile during its flights is it's attraction due to gravity. This force is constant and always directed vertically downwards, and causes the projectile to continually deviate from a straight line path to follow a parabolic path.

6

Is there a driving force acting to keep a projectile moving through the air?

No, this is a common misconception. The only force acting on the a being thrown in the air is the forces of gravity and air resistance.

7

What is Centripetal Force?

It is the force that acts on a body at 90* to the motion of the body, such that it causes the body to move in a circular path. The direction of the centripetal force is towards the centre of the circular path.

8

What does Newton's First Law state?

It states that an object will continue with its velocity unless acted upon by an external, unbalanced force. So if an object is stationary, it will remain stationary; if it is moving, it will continue to move unless a force causes it to accelerate.

9

How does Safety Factor work?

When calculating the force to be withstood by the attachments holding a horse onto a carousel, or restraints on any other ride, safety standards usually require that the actual force that can be withstood must be several times larger than the actual force.

A safety factor of 10 means 10 times the expected force must be able to be withstood.

10

If air resistance is ignored, what forces act upon the projectile?

The only force acting on a projectile during its flights is it's attraction due to gravity. This force is constant and always directed vertically downwards, and causes the projectile to continually deviate from a straight line path to follow a parabolic path.

11

Is there a driving force acting to keep a projectile moving through the air?

No, this is a common misconception. The only force acting on the a being thrown in the air is the forces of gravity and air resistance.

12

What is Conical Pendulum?

This system occurs when an object is not possible to be horizontal, although as the speed increases, the closer to horizontal it becomes.

13

What is Newton's Third Law?

It states that for ever action [force] there is an equal and opposite reaction [force].

13

What is an Apparent weight?

It is the weight force that you feel. Your apparent weight can change depending on the acceleration of the surface on which you are standing.

13

How does Newton's 3rd law apply to a car in a race track?

The reaction force of the track on the car balance the into-the-slope component of the force due to gravity on the car and therefore they cancel each other out, resulting in no acceleration of the car into the slope.

14

What is the Law of Conservation of Energy?

It states that energy can neither be created nor destroyed; it can only change form.

15

What is Kinetic Energy?

It is the energy an object has due to its motion.

16

Will you travel faster, slower or at the same max speed if you are the only person on a roller-coaster ride, compared with sharing the ride with nine other people? (Ignore the effect of friction.)

Anh

17

What is Newton's 2nd Law?

It states that the accelerating force on a body is equal to the rate of change of momentum of the body. The equation describing this can be manipulated to become force = mass x acceleration

17

What is the Action Force?

It is the initiating force, the force that is delivered by actions of a person.

18

What is Reaction Force?

It occurs equally and oppositely due to the action force. If the action force did not exist, then there would be no reaction force.

19

Explain the term Inertia.

It is a property of a body that is related to mass. It causes objects to oppose any change in velocity. Newton's first law is often called the law of inertia.

20

What is an Impulse?

It is the change in momentum of an object. It is also the product or the force and the time period over which the force acts.

21

Explain Seat Belts.

Increasing the time taken to stop your body means that smaller force is required to achieve the same change in momentum. A smaller force means that less damage is done to you.

22

How does a seatbelt with a larger area affect a person?

If the surface area of a seatbelt increases, it will reduce the pressure on the person's body during the period of time that the force is acting, as pressure is equal to the force applied divided by the area over which the force is acting; therefore the larger the area the lower the pressure.

23

Define the term Centrifugal force.

Eg. Driving round a corner. The centripetal force of the door on you is the action and the reaction force is you on the door; this force is the centrifugal force. But this is not the one that causes you to turn in a circular path; the centripetal force is the on that does that!

24

Why is there very few loop-the-loops in roller coasters?

As there is a loss of kinetic energy as the coaster increases in height, there is a corresponding decrease in speed and therefore a decrease in the centripetal force.

25

Why does the centripetal force have to remain firm at the top of a loop-the-loops?

So that we feel firm contact with the seat.

26

What happens when the radius of a loop-the-loop is reduced?

The centripetal force is increased. So if we can reduce the radius of the loop as the roller coaster travels yo the loop, then the centripetal force can remain constant even though the speed is decreasing.

On the way down, the radius increases so that the centripetal force is reduced as the coaster gains speed again.

Clothoid loop