Question

(b) At a certain instant, a body of mass
10 kg, falling freely under the force of
gravity, was found to be falling at the
rate of 20 m/s. What force will stop the
body in (i) 2 seconds and (ü) 2 metres?
5​

Answer 1

Answer:

Given:

Mass of object = 10kg

Velocity = 20m/s

To find:

Force required to stop the object in

i) 2 seconds

ii) 2 metres

Concept:

In both cases, we need to find the retardation (negative acceleration) to be provided .

Once we obtain the acceleration, we can multiply it with Mass to get the force.

Formulas used:

1. F = m × a

2. v² = u² + 2as

3. v = u + at

Calculation:

First case:

v = u + at

=> 0 = 20 + a × 2

=> a = - 20/2

=> a = -10 m/s²

So force = m × a =( -10) × 10

=> F = -100 N.

2nd case:

v² = u² + 2as

=> 0² = 20² + 2 × a × 2

=> 4a = -400

=> a = -100 m/s²

So, force = m × a =10 × (-100)

=> F = -1000 N.

Answer 2

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