Question

1. A net force of 15 N is exerted on an encyclopedia to cause it to accelerate at a rate of 5 m/s². Determine the mass of the encyclopedia.

2. A car of mass 250kg applied brakes to cause it's change in velocity from 16 m/s to 4m/s in 2 seconds. What force must be applied by the brakes?


3. A cyclist is travelling at 15m/s. She applies brakes so that she does not collide with a wall 18m away. What force must the brakes apply on the wheels?


4. Suppose that a table is accelerating at a rate of 2 m/s² If the net force is tripled and the mass is halved, then what is the new acceleration of the table?


5. A 5.0 kg mass has its velocity change from 8.0 m/s east to 2.0 m/s east. 
Find the object's change in momentum.​

Answer 1

1. A net force of 15 N is exerted on an encyclopedia to cause it to accelerate at a rate of 5 m/s².

So, mass of encyclopaedia is :

$mass= \dfrac{force}{accelertion}$

$\implies \: mass = \dfrac{15}{5}$

$\implies \: mass = 3 \:kg$

So, mass is 3 kg.

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2. Force applied = mass × acceleration

=> Force = m × (v-u)/t

=> Force = 250 × (4-16)/2

=> Force = 250 × (-6)

=> Force = -1500 N.

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3. First, let's find acceleration:

v² = u² + 2as

=> 0² = 15² + 2a(18)

=> 36a = -225

=> a = - 6.25 m/s²

So, force is : F = m × a = -6.25m N.

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4. Initial acceleration (a)= F/m = 2 m/s²

Now, new acceleration = 3F/(m/2) = 6a = 12 m/s².

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5. Let change in momentum be ∆P.

∆P = m ∆v

=> ∆P = 5 × (2 -8)

=> ∆P = 5 × (-6)

=> ∆P = -30 kg m/s

$\star$ Hope It Helps.

Answer 2

A net force of 15 N is exerted on an encyclopedia to cause it to accelerate at a rate of 5 m/s². Determine the mass of the encyclopedia