Question

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A tennis player bounces a tennis ball downwards with her racket. determine how fast the tennis ball is moving after it has moved 0.5 m downwards, assuming it was initially moving downwards at 4 m/s and accelerates downwards at 10m/s^2

Answer 1

• Initial velocity=u=4m/s
• Acceleration=a=10m/s^2
• Distance=s=0.5m
• Final velocity=v=?

Apply third equation of kinematics

`\\ \tt\hookrightarrow v^2=u^2+2as`

`\\ \tt\hookrightarrow v^2=4^2+2(10)(0.5)`

`\\ \tt\hookrightarrow v^2=16+10`

`\\ \tt\hookrightarrow v^2=26`

`\\ \tt\hookrightarrow v\approx 5m/s`

Answer 2

The tennis ball is moving 6m/s.

Step-by-step explanation:

displacement(s) = 0.5 m

intial velocity(u) = 4 m/s

acceleration(a) = 10 m/s²

As we know,

2as = v²-u²

or, 2 ×10 × 0.5 = v²-4²

or, 10 = v²-16

so, v² = 36

so, v (final velocity) = 6 m/s