motion (topic 5)

Question 1

calculate the acceleration of the car between C and D

Answer 1

Question 2

describe the motion of the car between B and C

Answer 2

constant speed/velocity of 12 m/s

Question 3

calculate the distance travelled between A and C

Answer 3

Question 4

describe how the forces acting on the skydiver vary as they fall (4)

Answer 4

• weight acts downwards
• initially air resistance is negligible/zero
• as the speed of the skydiver increases, air resistance increases
• terminal velocity is reached when the weight of the skydiver is equal to the air resistance

Question 5

explain how a parachute allows the skydiver to land safely (4)

Answer 5

• when the parachute is opened, the air resistance acting on the skydiver increases (so air resistance is greater than weight)
• this causes the skydiver to decelerate
• as the skydiver decelerates, air resistance decreases
• when weight is equal to the air resistance again, a new lower terminal velocity is reached

Question 6

calculate Jacks speed between 16 and 28 minutes

Answer 6

Question 7

convert 1,300 km/h to m/s

Answer 7

Question 8

explain why the car reaches a top speed (3)

Answer 8

• as the car accelerates, the air resistance increases
• reducing the resultant force acting on the car
• when the thrust is equal to the drag forces, the acceleration is zero and the car travels at a constant speed

Question 9

calculate the distance travelled by the athlete during the period of acceleration at the start of the race

Answer 9

Question 10

this roller coaster reaches a top speed of 26 m/s in 22.5 m, calculate the acceleration of the roller coaster at the start of the ride

Answer 10

Question 11

the mass of a passenger is 70kg, calculate the force exerted on the passenger during the initial acceleration 15m/s^2

Answer 11

Question 12

state the resultant force acting on the roller coaster cart at 25 s, give a reason for your answer (3)

Answer 12

• 0 N
• the roller coaster is travelling at constant speed, therefore zero acceleration
• with no acceleration, the resultant force is zero as given by F = m x a

Question 13

calculate the distance travelled by the roller coaster between 10 s and 20 s

Answer 13

Question 14

describe the motion of the stone from A to B (3)

Answer 14

• stone leaves the water surface at -6 m/s at 0 s
• stone decelerates and reaches the top of the bounce at 0.6 s
• stone accelerates downwards and hits the water again at 1.2 s

Question 15

calculate the maximum height reached by the stone above the water surface

Answer 15

• distance travelled is equal to the area
• area = 0.5 x 6 x 0.6 = 1.8 m

Question 16

Answer 16

• the stone does not travel as far
• smaller area under graph = lower distance travelled
• lower height of second bounce

Question 17

calculate the acceleration of the stone between 1.2 and 1.8 s

Answer 17

Question 18

the length of the ramp was 2 m, calculate the acceleration of the trolley when the starting height of the ramp was 20 cm

Answer 18

Question 19

the plane has the engines set to maximum thrust for the duration of take off, explain why the acceleration of the plane is not constant (3)

Answer 19

• initially there is a high acceleration due to low air resistance
• as speed increases, air resistance increases
• when air resistance is equal to the thrust forces of the engines, maximum speed is reached

Question 20

calculate the acceleration of the plane during the first 2 seconds

Answer 20

Question 21

the maximum thrust of the engines is 1,800 kN, the mass of the plane is 120,000 kg, calculate the maximum mass of passengers, fuel and luggage for the plane to achieve the acceleration calculated in part c

Answer 21