Physics - Study Mode

[#656] A mass of 20 kg is at a height of 8 m above the ground. Then the potential energy possessed by the body is: [Given g = 9.8 m/s 2 ]
Correct Answer

(A) 1568 J

Explanation

Solution: A mass of 20 kg is at a height of 8 m above the ground. Then the potential energy possessed by the body is 1586 J.

[#657] A person lifts luggage of 20 kg from the ground and puts it on his head 2m above the ground. Calculate the work done by him. (g = 10 )
Correct Answer

(B) 400J

Explanation

Solution: Total work done in lifting and moving the luggage is 588 Joules. Explanation : 1. work done in lifting the luggage = potential energy of the luggage = mgh where, m = mass = 20 kg g = acceleration due to gravity = 9.8 m/s² h = height = 3 m Hence, P = mgh = 20 x 9.8 x 3 = 588 J 2. work done in moving the object, Since now weight of the luggage is acting in downward direction and the movement is in horizontal direction, hence work done in moving the luggage is zero because component of force along horizontal direction is zero. Total work done = 588 + 0 = 588 J. Hence total work done in lifting and moving the luggage 588 J.

[#658] Work done in a free expansion process is
Correct Answer

(B) 0

Explanation

Solution: In free expansion there is no work done as there is no external external pressure. That's certainly true, in fact free expansion is an irreversible process in which a gas expands into an insulated evacuated chamber, you can think of it like ann container with a piston and the gas is left to expand in vacuum.

[#659] An object of 10 kg is moving with a speed of 2 m/s. The kinetic energy of the object is
Correct Answer

(A) 20 J

Explanation

Solution: Kinetic energy = 1/2mv 2 = 1/2*10*2 2 = 1/2*10*4 = 5*4 = 20 J

[#660] If both the mass and the velocity of a body is increased to twice of their magnitude, the kinetic energy will increase by
Correct Answer

(C) 8 times

Explanation

Solution: If you double mass and double velocity, you get eight times the kinetic energy, no matter what your first energy is. As an object's kinetic energy increases, and momentum is mass x velocity.