# Power, Force and Velocity

## Trending Questions

**Q.**A force (4^i+^j−2^k) N acting on a body maintains its velocity at (2^i+3^j−^k) m/s. The power exerted is

- 15 W
- 13 W
- 12 W
- 20 W

**Q.**A ball of mass 5 kg is dropped from a tower. Find the power of gravitational force at time t=2 seconds.

(Take g=10 m/s2)

- 1000 W
- 2000 W
- 100 W
- 200 W

**Q.**A particle of mass m starts moving in a circular path A of constant radius r in such a way that its centripetal acceleration ac is changing with time as ac=k2r2t2 where k is a constant. What is the power delivered to the particle by the force acting on it?

- mk2r4t2
- mk2r2t2
- mk2r3t
- mkr4t2

**Q.**

In the streamlined flow of a liquid, the power due to the pressure difference between the ends of the tube is

Equal to a product of pressure and volume of liquid flowing per second.

Equal to a product of pressure and mass of liquid flowing per second.

Equal to the product of radius and coefficient of viscosity.

Equal to the product of pressure and velocity.

**Q.**A boy whose mass is 30 kg climbs with a constant speed on a vertical rope of 6 m length in 10 s. The power of the boy during the climb is

(Take g=10 m/s2)

- 60 W
- 3000 W
- 180 W
- 5 W

**Q.**A particle of mass 0.2 kg (initially at rest) starts moving in one dimension under a force that delivers a constant power 0.5 W to the particle. Then the speed after 5 seconds is

- 20 m/s
- 5 m/s
- 10 m/s
- 20 m/s

**Q.**A body of mass 5 kg starts from rest and moves in a straight line under the influence of two variable forces F1=(10t+6t) N and F2=(15−6t) N, acting in same direction. Find the power delivered by force F1 at t=2 sec.

- 130 J/s
- 230 J/s
- 30 J/s
- 350 J/s

**Q.**A car of 100 HP is moving with a constant velocity of 72 km/hour. The forward force exerted by the engine of the car is

- 3.73×103 N
- 3.72×102 N
- 3.73×101 N
- None of the above

**Q.**Figure shows an ideal spring block system, force constant of spring is k which has been compressed by an amount x0. If x is instantaneous deflection of spring from its natural length, mark the correct option (s).

- Instantaneous power developed by spring is P=kx√km(x20−x2)
- Maximum power of spring is k2√kmx20
- Maximum power occurs at x=x0√2
- Maximum power occurs at x=x02

**Q.**In unloading grain from the hold of a ship, an elevator lifts the grain through a height of 12 m. Grain is discharged at the top of the elevator at a rate of 2 kg/s, and the discharge speed of each grain particle is 3m/s. Then, the minimum power of the motor that can elevate grain in this way is

- 149 W
- 249 W
- 100 W
- 549 W

**Q.**A particle of mass 0.2 kg is moving in one dimension under a force that delivers a constant power 0.5 W to the particle. If the initial speed (in m/s) of the particle is zero, then speed in (m/s) after 5 s is

- 2.5 m/s
- 5 m/s
- 10 m/s
- 3 m/s

**Q.**An electric motor produces a tension of 4500N in a load lifting cable and rolls it at the rate of 2m/s. The power of the motor is

- 9 kW
- 15 kW
- 225 kW
- 9×103 hp

**Q.**An advertisement claims that a certain 1200 kg car can accelerate from rest to a speed of 25 m/s in a time of 8s. What average power must the motor produce to cause this acceleration? (Ignore friction losses)

- 46.9 kW
- 56.9 kW
- 76.9 kW
- Zero

**Q.**A mass m falls from rest under the influence of gravity. Then the average power supplied to the mass by the force of gravity is

- P=m√g3h3
- P=m√g3h12
- P=2m√g3h2
- P=m√g3h2

where h is the distance the mass falls.

**Q.**What is the power required by the pump to lift 1000 kg of water per minute from a 20 m deep well and eject it with the speed of 20 m/s?

- 3666.7 W
- 4666.7 W
- 6666.7 W
- 5666.7 W

**Q.**Water from a stream is falling on the blades of a turbine at the rate of 100kg/sec. If the height of the stream is 100m then the power delivered to the turbine is

- 100 kw
- 100 w
- 10 kw
- 1 kw

**Q.**Power supplied to a particle of mass 2 kg varies with time as p=3t22 watt. Here 't' is in second. If velocity of particle at t = 0 is v = 0. The velocity of particle at time t = 2 second will be

- 1 m/s
- 4 m/s
- 2 m/s
- 2√2 m/s

**Q.**A body at rest starts moving under the action of a constant force along a straight line. The instantaneous power developed by this force with time t is correctly represented by

**Q.**Water from a stream is falling on the blades of a turbine at the rate of 100kg/sec. If the height of the stream is 100m then the power delivered to the turbine is

- 100 kw
- 100 w
- 10 kw
- 1 kw

**Q.**A hoist operated by an electric motor has a mass of 500 kg. It raises a load of 300 kg vertically at a steady speed of 0.2 m/s. Frictional resistance can be taken to be constant at 1200 N. What is the power required?

- 1.51 kW
- 1.81 kW
- 2.01 kW
- 1.61 kW

**Q.**A body is being moved along a straight line by a machine delivering a constant power. The distance covered by the body in time t is proportional to

- √1
- t3/2
- t3/4
- t2

**Q.**A force F acting on a body depends on its displacement x as F∝x−13. The power delivered by F will depend on displacement as

- x23
- x53
- x12
- x0

**Q.**A man is pulling a block resting on the ground by applying force F=(20t+40) N as shown in the figure. If the pulley is frictionless and mass of the block is 4 kg, find out the power delivered by the force, 3 seconds after the man starts pulling the block. (Take g=10 m/s2)

- 2250 J/s
- 5250 J/s
- 3000 J/s
- 1250 J/s

**Q.**A force (4^i+^j−2^k) N acting on a body maintains its velocity at (2^i+3^j−^k) m/s. The power exerted is

- 15 W
- 13 W
- 12 W
- 20 W

**Q.**A constant power P is applied to a particle of mass m. The distance travelled by the particle when its velocity increases from v1 to v2 is - (neglect friction)

- 3Pm(v22−v21)
- m3P(v2−v1)
- m3P(v32−v31)
- m3P(v22−v21)

**Q.**An engine generates a power of 75 kW having efficiency of 80% and the car moves with a constant velocity of 20 m/s. Find the force generated by the engine. (Assume the engine applies a constant force on the car)

- 2000 N
- 3000 N
- 6000 N
- 1500 N

**Q.**A 40 kg girl is swinging on a swing from rest. Then, the power delivered when moving with a velocity of 2 m/s upwards in a direction making an angle 60∘ with the vertical is

- 248√3 W
- 392√3 W
- 448 W
- 580 W

**Q.**A block of mass 2 kg initially at rest moves under the influence of a time-dependent force →F=4t N ^i. The power developed by the force at t=2 second is

- 16 W
- 32 W
- 48 W
- 30 W

**Q.**A particle of mass m starts moving in a circular path A of constant radius r in such a way that its centripetal acceleration ac is changing with time as ac=k2r2t2 where k is a constant. What is the power delivered to the particle by the force acting on it?

- mk2r4t2
- mk2r2t2
- mk2r3t
- mkr4t2

**Q.**Power supplied to a particle of mass 5 kg varies with time as P=4t35 W, where t is in seconds. If the velocity of the particle at t=0 is zero, then what will be the velocity of the particle at 5 seconds?

- 5√2 m/s
- √2 m/s
- 5 m/s
- 2 m/s