# physics

just a couple more questions

1.) The power needed to accelerate a projectile from rest to is launch speed v in a time t is 43.0 W. How much power is needed to accelerate the same projectile from rest to launch speed of 2v in a time of 1/2t?

2.)A ball is fixed to the end of a string , which is attached to the eiling at point P, which is at the top. the ball is positioned below it, what enables it to go back to point P? Hope this makes sense. Like swinging the ball basically

1. 👍
2. 👎
3. 👁
1. 1) You need to produce four times the kinetic energy (because of the V^2 dependence) in half the time. What does that tell you about the power required?

2) When the ball is below what? It cannot return to the ceiling from below unless it is given sufficient kinetic energy.

1. 👍
2. 👎
2. The velocity would be four times as great and the time would be two times as great. So the power would be (43)(4)(2)=344 watts

1. 👍
2. 👎
3. Well you see the coefficient of friction is zero and the air resistance is too strong thus the projectile would go the speed of light and end the entire human race as we know it would come to an end. It would be better to not accelerate that object. Dinosaurs extinction is based on the theory of this problem. Once the velocaraptor figured out how fast it would take he killed them all off

1. 👍
2. 👎

## Similar Questions

1. ### Physics

The average person passes out at an acceleration of 7g (that is, seven times the gravitational acceleration on Earth). Suppose a car is designed to accelerate at this rate. How much time would be required for the car to accelerate

2. ### physics

The highest barrier that a projectile can clear is 12.7 m, when the projectile is launched at an angle of 17.5° above the horizontal. What is the projectile's launch speed?

3. ### physics

what average force is needed to accelerate a 7.00-gram pellet from rest to 125m/s over distance of a .800m along the barrel of a rifle.

4. ### physics

How strong an electric field is needed to accelerate electrons in a TV tube from rest to one-tenth the speed of light in a distance of 4.9 cm ?

1. ### physics

a jet plane lands with a speed of 101 m/s and can accelerate at a maximum rate of -4.60 m/s2 as it comes to rest. (a) From the instant the plane touches the runway, what is the minimum time needed before it can come to rest? ___s

2. ### physics

A jet plane lands with a speed of 81 m/s and can accelerate at a maximum rate of −5.00 m/s2 as it comes to rest. (a) From the instant the plane touches the runway, what is the minimum time needed before it can come to rest? (b)

3. ### physics

A light–rail commuter train draws 645 A of 590–V DC electricity when accelerating. What is its power consumption rate in kilowatts? How long does it take to reach 30.0 m/s starting from rest if its loaded mass is 4.50×104 kg,

4. ### physics

A 1000 kg car can accelerate from rest to a speed of 25 m/s in 10 s. What average power must the engine of car produce in order to cause this acceleration? Neglect friction losses

1. ### physics

A jet plane lands with a speed of 87 m/s and can accelerate at a maximum rate of -5.30 m/s2 as it comes to rest. (a) From the instant the plane touches the runway, what is the minimum time needed before it can come to rest? What

2. ### physics

Scientists are experimenting with a kind of gun that may eventually be used to fire payloads directly into orbit. In one test, this gun accelerates a 7.0 kg projectile from rest to a speed of 4.0 x 103 m/s. The net force

3. ### PHYSICS

dETERMINE the horizontal force needed to accelerate a 50 kg grocery cart from rest to 0.90 m/s in 2.8s if the coefficient of friction between the cart and the floor is 0.20?

4. ### Physics

A jet plane lands with a speed of 110 m/s and can accelerate with a maximum magnitude of 7.00 m/s2 as it comes to rest. (a) From the instant the plane touches the runway, what is the minimum time interval needed before it can come