DP Physics (last assessment 2024)

Question 21M.2.SL.TZ2.1

Date	May 2021	Marks available	[Maximum mark: 10]	Reference code	21M.2.SL.TZ2.1
Level	SL	Paper	2	Time zone	TZ2
Command term	Calculate, Deduce, Outline, State	Question number	1	Adapted from	N/A

[Maximum mark: 10]

21M.2.SL.TZ2.1

A football player kicks a stationary ball of mass 0.45 kg towards a wall. The initial speed of the ball after the kick is 19 m s⁻¹ and the ball does not rotate. Air resistance is negligible and there is no wind.

(a)

The player’s foot is in contact with the ball for 55 ms. Calculate the average force that acts on the ball due to the football player.

[2]

Markscheme

$Δ p = 0.45 \times 19 OR a = \frac{19}{0.055}$ ✓

$« = F = \frac{0.45 \times 19}{0.055} » 160 « N »$ ✓

Allow [2] marks for a bald correct answer.

Allow ECF for MP2 if 19 sin22 OR 19 cos22 used.

(b.i)

The ball leaves the ground at an angle of 22°. The horizontal distance from the initial position of the edge of the ball to the wall is 11 m. Calculate the time taken for the ball to reach the wall.

[2]

Markscheme

$horizontal speed = 19 \times \cos 22 « = 17.6 {m s}^{- 1} »$ ✓

$time = « \frac{distance}{speed} = \frac{11}{19 \cos 22} = » 0.62 « s »$ ✓

Allow ECF for MP2

(b.ii)

The top of the wall is 2.4 m above the ground. Deduce whether the ball will hit the wall.

[3]

Markscheme

$initial vertical speed = 19 \times \sin 22 « = 7.1 {m s}^{- 1} »$ ✓

$« 7.12 \times 0.624 - 0.5 \times 9.81 \times 0 . 624^{2} = » 2.5 « m »$ ✓

ball does not hit wall OR 2.5 «m» > 2.4 «m» ✓

Allow ECF from (b)(i) and from MP1

Allow g = 10 m s⁻²

(c)

In practice, air resistance affects the ball. Outline the effect that air resistance has on the vertical acceleration of the ball. Take the direction of the acceleration due to gravity to be positive.

[2]

Markscheme

air resistance opposes «direction of» motion
OR
air resistance opposes velocity ✓

on the way up «vertical» acceleration is increased OR greater than g ✓

on the way down «vertical» acceleration is decreased OR smaller than g ✓

Allow deceleration/acceleration but meaning must be clear

(d)

The player kicks the ball again. It rolls along the ground without sliding with a horizontal velocity of $1.40 {m s}^{- 1}$ . The radius of the ball is $0.11 m$ . Calculate the angular velocity of the ball. State an appropriate SI unit for your answer.

[1]

Markscheme

$13 « rad » s^{- 1}$ ✓

Unit must be seen for mark

Accept Hz

Accept $4 π « rad » s^{- 1}$

Syllabus sections

Core

Core » Topic 2: Mechanics » 2.4 – Momentum and impulse

Core » Topic 2: Mechanics

Core » Topic 2: Mechanics » 2.1 – Motion

Core » Topic 6: Circular motion and gravitation » 6.1 – Circular motion

Core » Topic 1: Measurements and uncertainties » 1.1 – Measurements in physics

Core » Topic 1: Measurements and uncertainties

Core » Topic 6: Circular motion and gravitation

Question 21M.2.SL.TZ2.1

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