A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a leveled road. The work done against the gravitational force will be (g =10 m s–2)
The type of energy possessed by a simple pendulum, when it is at the mean position is:
In a simple pendulum with no friction, mechanical energy is conserved. Total mechanical energy is a combination of kinetic energy and gravitational potential energy. As the pendulum swings back and forth, there is a constant exchange between kinetic energy and gravitational potential energy.
In case of negative work the angle between the force and displacement is:
Work done W = F.d cos 0
∴Work done at θ= 0°, W = F.d cos 0° (∴cos0° = 1)
⇒ W = F.d
For angle θ = 0°,
Work done Is positive, so it is not true.
(b) We know that work done, W = F .d cos 0
For angle 0 = 45°,
work done is positive, so it is not true.
(c) We know that work done, W = d cos θ
Work done at θ = 90°, W = F.d cos 90° (∴cos 90° = 0)
W = 0
So, it is not true.
(d) Work done at θ = 180°, W = F.d cosθ (∴ cos 180°= -1)
W = - F. d
For negative work, the angle between the force and displacement should be 180°. (/.e„ force and displacement are anti parallel to each other) So, it is true.
How are Joule (J) and ergs (erg) related?
A 1 kg mass has a kinetic energy of 1 joule when its speed is:
K.E = 1/2 m v^2
1 = 1/2 * 1 * v^2
2 = v^2
v^2 = 2
v = √2