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4 years ago

On Earth a ball is thrown straight downward with an initial speed of 1 meter

1 answer:

Montano1993 [528]4 years ago

7 0

-- Gravity adds 9.8 m/s to the downward speed of any object, every second ... as long as there are no other forces messing with it.

-- In 0.6 sec, gravity added (0.6x9.8)= 5.88 m/s to the downward speed of this ball.

-- This ball didn't start from zero. You threw it down with an initial speed of 1 m/s. So after 0.6 sec, with the help of gravity, its speed is

(1) + (5.88) = 6.88 m/s .

Pick choice-C .

Notice that we don't care how high it was off the ground when you threw it, just as long as it was high enough to keep falling for 0.6 sec without hitting the ground.

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1. Potential energy and a roller coaster. A 1000-kg roller coaster car moves from point A to B then C.

zalisa [80]

Answer:(a) With our choice for the zero level for potential energy of the car-Earth system when the car is at point B ,

When the car is at point A, the potential energy of the car-Earth system is given by

=mgy

where y is the vertical height above zero level. With 135ft=41.1m, this height is found as:

y=(41.1m)sin40.0

=26.4m

Thus,

=(1000kg)(9.80m/s

)(26.4m)=2.59∗10

The change in potential energy of the car-Earth system as the car moves from A to B is

−U

=0−2.59∗10

J=−2.59∗10

(b) With our choice of the zero configuration for the potential energy of the car-Earth system when the car is at point A, we have U

=0. The potential energy of the system when the car is at point B is given by U

=mgy, where y is the vertical distance of point B below point A. In part (a), we found the magnitude of this distance to be 26.5m. Because this distance is now below the zero reference level, it is a negative number.

Thus,

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2 years ago

1)A rocket expels gas at high speed for a short period of time. We are going to treat the rocket as being far away from any grav

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3 years ago

3) A driver in a 1000-kg car traveling at 24 m/s slams on the brakes and skids to a stop. If the coefticient of friction between

Natali5045456 [20]

Answer:

A) 37 m

Explanation:

The car is moving of uniformly accelerated motion, so the distance it covers can be calculated by using the following SUVAT equation:

$v^2 -u^2 = 2ad$ (1)

where

v = 0 m/s is the final velocity of the car

u = 24 m/s is the initial velocity

a is the acceleration

d is the length of the skid

We need to find the acceleration first. We know that the force responsible for the (de)celeration is the force of friction, so:

$F=ma=-\mu mg$

where

m = 1000 kg is the mass of the car

$\mu = 0.80$ is the coefficient of friction

a is the deceleration of the car

g = 9.8 m/s^2 is the acceleration due to gravity

The negative sign is due to the fact that the force of friction is against the motion of the car, so the sign of the acceleration will be negative because the car is slowing down. From this equation, we find:

$a=-\mu g$