Chapter 8 - On the move

Question 1

What does the gradient of a displacement - time graph represent?

Answer 1

Speed of the object

Question 2

What does a curved line on a displacement - time graph show?

Answer 2

Changing speed

Question 3

What is uniform acceleration?

Answer 3

Where velocity of object moving along a straight line change at a constant rate.

Question 4

What is non-uniform acceleration?

Answer 4

Where the direction of motion of an object changes, or its speed changes at a varying rate.

Question 5

What does the gradient of a velocity - time graph show?

Answer 5

Acceleration

Question 6

What equations are used for motion with constant acceleration?

Answer 6

SUVAT equations

Question 7

What does each letter in Suvat represent?

Answer 7

S - distance
U - initial velocity
V - final velocity
A - acceleration 
T - time

Question 8

Give all 5 suvat equations

Answer 8

v = u +at
s = 1/2(u+v)t
s = ut + 1/2at^2
s = vt - 1/2at^2
v^2 = u^2 +2as

Question 9

What does the area under a velocity - time graph represent?

Answer 9

Distance/ displacement

s = v x t

Question 10

What does area under acceleration - time graph represent?

Answer 10

Change in velocity

change in velocity = acceleration x time

Question 11

What is the acceleration of a falling object (free fall)?

Answer 11

9.8 ms^-2

Question 12

Describe a displacement - time graph for a ball thrown upwards 2m and moves back down

Answer 12

displacement increases at accelerating rate until maximum (2m and 2s) then decreases to 0 at same rate as it went up

Question 13

What is a projectile?

Answer 13

Any object acted upon by the force of gravity

Question 14

What are the 3 key principles that apply to projectiles?

Answer 14

• Acceleration of the object is always equal to g (9.8ms^-2)
• Horizontal velocity of object is constant as acceleration has no horizontal component.
• Motions in horizontal and vertical directions are independent of each other.

Question 15

If 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?

Answer 15

Both hit the floor at the same time as horizontal velocity is irrelevant in projectiles.

Question 16

What happens to a projectile if it’s initial projection is horizontal?

Answer 16

• It’s path through the air becomes steeper and steeper as it drops.
• The faster it is projected the further away it will hit the ground
• Does not effect time taken to drop to the ground

Question 17

Does air resistance increase or decrease with speed? And why?

Answer 17

Increases with speed as more air particles collide with surface.

Question 18

What are the effects of air resistance on a projectile?

Answer 18

• Has horizontal component that reduces both horizontal speed of the projectile and its range.
• Reduces the maximum height of the projectile if its initial direction is above the horizontal.
• Makes descent steeper than ascent.

Question 19

What is a drag force?

Answer 19

Force caused by friction between layers of air near the projectile’s surface.