Chapter 7 Flashcards

Question

Weight = what?

Answer 1

Mass x gravity

Answer 2

Mass x acceleration | Newtons second law

Answer 3

Heavy objects typically fall faster in air vac use air resistant = cross sectional area = r² Weight = mass = volume = r³

Answer 4

Wave going up then down then up | Like a transverse wave but going up

Answer 5

Goes up then down like a shape of a hill

Answer 6

V shape graph that is a straight line Example Going from 10 on the y axis to 0 on the y axis and then going back up in a straight line but NOT virtual diagonal line

Answer 7

Y axis going from POSITIVE to NEGATIVE a straight line down diagonally

Answer 8

If distance increases with time as there isn’t really any such things as negative distance due to its scalar nature

Answer 9

It ends a zero due to its vector nature. This plots a similar parabola y = -ax² + bx + c

Answer 10

This is because of -9.81 ( gravity) and the displacement when v>0 = displacement when v<0 ( area under line)

Answer 11

Velocity Δy/Δx =Δs/T = velocity

Answer 12

1. Acceleration 2. displacement Δy/Δx = Δv/T = acceleration Y x X = v x T = displacement

Answer 13

Projectile motion = horizontal motion + vertical motion

Answer 14

Horizontal place we simply use v=s/T as there is no acceleration

Answer 15

Treated as a free fall question

Answer 16

``` Vertical = Suvat Horizontal = v=s/T So for horizontal you need the horizontal line from the triangle and the Suvat answer Suvat = T Horizontal = s ```

Answer 17

V = 2 x π × r / T Where T is the time to move round once and 2 x π x r is the circumference of the circle.

Answer 18

As charge of velocity per unit time

Answer 19

Uniform acceleration is where the velocity of an object moving along a straight line changes at a constant rate. In other words the acceleration is constant. ``` A= v-u / t V = initial U = final ```

Answer 20

Speed y axis Time x axis When an object is moving at a constant velocity. S = v x t Straight line horizontal

Answer 21

``` Speed = y axis Time = x axis ``` Consider an object at constant acceleration (a) from initial velocity (u) to velocity (v) at time (t) Equation = s= (u+v) x t / 2 (Suvat equation ) Graph Diagonal line from lowest point on y axis to the highest point on x axis Middle of y axis is the average speed

Answer 22

When an object is changing acceleration, let v represent the velocity at time t and (v+δv) (δ = delta ) Represent the velocity a short time later at (t+δt). Graph So it’s a (s) graph but the (s) is horizontal V+δv is above v So is the same with time Displacement = area under the line of velocity time graph Example like a constant velocity Area = (6 y axis) x (5 x axis) = 30m Distance = 30m

Answer 23

Release a stone and a small coin at the same time. Which one hits ine ground first? The answer to this question was first discovered by calileo Galileli about tour centuries ago. He reasoned that because any number of identical objects must fall at the same rate, then any one such object must tall at the same rate as the rest put together. So he concluded that any two Objects must fall at the same rate, regardless of their relative weights.

Answer 24

Displacement is distance in a given direction from a certain point. Consider a ball thrown directly upwards and caught when it returns. If the ball rises to a maximum height of 2.0 m, on returning to the thrower its displacement from its initial position is zero. However, the distance it has travelled is 4.0 m. ``` Graph Semi circle graph Y axis = displacement X axis = time Highest point is the maximum point ``` Immediately after leaving the thrower's hand, the velocity is positive and large so the gradient is positive and large. As the ball rises, its velocity decreases so the gradient decreases. At maximum height, its velocity is zero so the gradient is zero. As the ball descends, its velocity becomes increasingly negative, corresponding to increasing speed in a downward direction. So the gradient becomes increasingly negative.

Answer 25

Distance graph The distance travelled by the object changes with time as shown by Figure 2. The gradient of this line represents the speed. From projection to maximum height, the shape is exactly the same as in Figure 1. After maximum height, the distance continues to increase so the line curves up, not down like Figure 1. Graph Y axis = distance X axis = time First half of the graph slowly projects upwards then the second half it projected further upwards Half way of the graph before being projected upwards half way is the maximum height Looks like a horizontal (s).

Answer 26

Velocity is speed in a given direction. Consider how the velocity of an object thrown into the air changes with time. The object's velocity decreases from its initial positive (upwards) value to zero at maximum height then increases in the negative (downwards) direction as it falls.

Answer 27

1 The gradient of the line represents the object's acceleration This is constant and negative, equal to the acceleration ot free fall, q. The acceleration of the object is the same when it descends as when it ascends so the gradient of the line is always equal to -9.8 ms-2 2 The area under the line represents the displacement of the object from its starting position. The area between the positive section of the line and the time axis represents the displacement during the ascent. The area under the negative section of the line and the time axis represents the displacement during the descent. Taking the area for a as positive and the area for b as negative, the total area is therefore zero. This corresponds to zero for the total displacement. Graph Positive to negative for y axis Maximum height occurs at time t = u / g

Answer 28

A projectile is any object acted upon only by the force of gravity

Answer 29

The acceleration of the object is always equal to g and is always downwards because the force of gravity acts downwards. The acceleration therefore only affects the vertical motion of the object.

Answer 30

The horizontal velocity of the object is constant because the acceleration of the object does not have a horizontal component.

Answer 31

The motions in the horizontal and vertical directions are independent of each other.

Answer 32

Such an object moves vertically as it has no horizontal motion. Its acceleration is 9.8 ms-2 downwards. Using the direction code + is upwards, - is downwards, its displacement, y, and velocity, v, after time t are given by V=u - gxt y=uxt - 1/2 x gxp

Answer 33

A stone thrown from a chilf top follows a curved path downwards before it hits the water. If its initial projection is horizontal its path through the air becomes steeper and steeper as it drops the faster it is projected, the further away it will fall into the sea the time taken for it to fall into the sea does not depend on how fast it is projected. Suppose two balls are released at the same time above a level floor such that one ball drops vertically and the other is projected horizontally. Which one hits the floor first? In fact, they both hit the floor simultaneously. They are both pulled to the ground by the force of gravity, which gives each ball a downward acceleration g. The ball that is projected horizontally experiences the same downward acceleration as the other ball. This downward acceleration does not affect the horizontal motion of the ball projected horizontally - only the vertical motion is affected,

Answer 34

The effects of air resistance A projectile moving through air experiences a force that drags on it because of the resistance of the air it passes through. This drag force is partly caused by friction between the layers of air near the projectile's surface where the air flows over the surface. The drag force: acts in the opposite direction to the direction of motion of the projectile, and it increases as the projectile's speed increases has a horizontal component that reduces both the horizontal speed of the projectile and its range reduces the maximum height of the projectile if its initial direction is above the horizontal and makes its descent steeper than its ascent.