A body of mass 2 kg, initially at rest, is moved by 3 m along the horizontal by a force of 10 N acting at an angle of 60° with the horizontal. The kinetic energy gained by the body is

Question

A body of mass 2 kg, initially at rest, is moved by 3 m along the horizontal by a force of 10 N acting at an angle of 60° with the horizontal. The kinetic energy gained by the body is (A) 15 J (B) 20 J (C) 25 J (D) 30 J

Tardigrade Admin · Accepted Answer

Component of force along the direction of displacement

= F cos θ = 10 \times cos 6 0^{°} = 5 N

Therefore, acceleration is

a = \frac{5 N}{2 k g} = 2.5 m s^{- 2}

As

υ^{2} - u^{2} = 2 a s

or

υ^{2} = 2 a s (∵ u = 0)

∴ K . E = \frac{1}{2} m υ^{2} = ma s = 2 \times 2.5 \times 3 = 15 J

Q. A body of mass 2 kg, initially at rest, is moved by 3 m along the horizontal by a force of 10 N acting at an angle of $6 0^{°}$ with the horizontal. The kinetic energy gained by the body is

$15 J$

$20 J$

$25 J$

$30 J$

Component of force along the direction of displacement $= F cos θ = 10 \times cos 6 0^{°} = 5 N$
Therefore, acceleration is
$a = \frac{5 N}{2 k g} = 2.5 m s^{- 2}$
As $υ^{2} - u^{2} = 2 a s$
or $υ^{2} = 2 a s (∵ u = 0)$
$∴ K . E = \frac{1}{2} m υ^{2} = ma s = 2 \times 2.5 \times 3 = 15 J$

Q. A body of mass 2 kg, initially at rest, is moved by 3 m along the horizontal by a force of 10 N acting at an angle of 60° with the horizontal. The kinetic energy gained by the body is

15J

20J

25J

30J