Work, Energy and Power

A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g = 10 ms²)

• 6 × 10³ J

• 6 J

• 0.6 J

• zero

Tags

NGSS.MS-PS3-2

The number of joules contained in 1 kWh is

• 36 × 10⁵ J

• 3.6 × 10⁷ J

• 36 × 10⁸ J

• 3.7 × 10⁷ J

Tags

NGSS.HS-PS3-1

Two army persons A and B each of weight of 500 N climb up a rope through a height of 10 m. A takes 20 s while B takes 40 s to achieve this task. What is ratio of the powers of person A and B?

• 1:2

• 1:4

• 2:1

• 14:1

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

If speed of a car becomes 2 times, its kinetic energy becomes

• 4 times

• 8 times

• 16 times

• 12 times

Tags

NGSS.MS-PS3-1

A cyclist comes to a skidding stop at 50 m. During this process, the force on the cycle due to the road is 1000 N and is directed opposite to the motion. How much work does the road do on the cycle?

• 5000J

• 500000J

• 50000J

• 10000J

Tags

NGSS.MS-PS2-2

A ball of mass 2kg is thrown up with a speed of 10m/s. Find the kinetic energy of the ball at the time of throwing.

• 50J

• 100J

• 99J

• 200J

Tags

NGSS.MS-PS3-1

NGSS.MS-PS3-4

Calculate the power of an electric motor that can lift 800 kg of water to store in a tank at a height of 1500cm in 20s. (g=10m/s²).

• 6kW

• 6W

• 6000kW

• 600W

Tags

NGSS.MS-PS3-5

Calculate the electricity bill amount for a month of 30 days, if the rate of electricity is 2.50 rupees per unit and the following devices are used as specified:

a. Two bulbs of 40W for six hours.

b. Two tubelights of 50W for eight hours.

c. A TV of 120W for six hours.

• Rs. 150

• Rs. 200

• Rs. 175

• Rs. 300

In a factory four bulbs of 100 W each and five fans of 110 W each operate for 12 hours daily. Calculate the units of electricity consumed?

• 9 units

• 15.5 units

• 12.2 units

• 11.4 units

A 1.5 m high person is holding a 20 kg trunk on his head and is standing at a roadways bus-terminal. How much work is done by the person?

• 9J

• 8J

• 0J

• 13J