IB Physics SL A.1.8 Projectile components

[Maximum number: 5]

A student strikes a tennis ball that is initially at rest so that it leaves the racquet at a speed of $64 \mathrm{~m} \mathrm{~s}^{-1}$ . The ball has a mass of 0.058 kg and the contact between the ball and the racquet lasts for 25 ms .

(a)

The student strikes the tennis ball at point P . The tennis ball is initially directed at an angle of $7.00^{\circ}$ to the horizontal.

The following data are available.

[ 5 ]

(i)

Calculate the time it takes the tennis ball to reach the net.

[ 2 ]

horizontal component of velocity is $64.0 \times \cos 7^{\circ}=63.52<\mathrm{ms}^{-1} \gg$ $t=<\frac{11.9}{63.52}=>0.187 / 0.19<\mathrm{s} \gg$

Marking guidance:

Do not award BCA. Check working. Do not award ECF from using $64 \mathrm{~m} \mathrm{~s}^{-1}$ .

(ii)

Show that the tennis ball passes over the net.

[ 3 ]

ALTERNATIVE 1
$u_{y}=64 \sin 7 / 7.80<\mathrm{ms}^{-1} \gg$

decrease in height $=7.80 \times 0.187+\frac{1}{2} \times 9.81 \times 0.187^{2} / 1.63$ «m»

final height = « 2.80-1.63 » =1.1 / 1.2 «m»

«higher than net so goes over»

ALTERNATIVE 2

vertical distance to fall to net «=2.80-0.91 »=1.89 «m»

time to fall this distance found using $<1.89=7.8 t+\frac{1}{2} \times 9.81 \times t^{2}$ »

t=0.21 «s»

0.21 «s» > 0.187 «s»

«reaches the net before it has fallen far enough so goes over»

Other alternatives are possible

IB Physics SL A 1 8 Projectile Components Questions

Exam points

IB Physics SL A 1 8 Projectile Components Questions question 1

Question (a)

Question (i)

Question (ii)