posted by .

A car is traveling at 20m/s when it pulls out to pass a truck that is traveling at only 18m/s. The car accelerates at 2.0m/s^2 for 4.0 s and then maintains this new velocity.

First it asked me to calculate the distance during acceleration so I used d = (v1)(t)+[(a)(t^2)]/2 and got 56 km.

Then it asked me to calculate the car's speed so I used V1+(a)(t) and got 28 m/s.

Now c) If the car was originally 8.0 m behind the truck when it pulled out to pass, how far in front of the truck is the car 10.0 s later?

------------------------------------------
A ball is thrown vertically upward from a window that is 3.6 m above the ground. The ball's initial speed is 2.8 m/s and the acceleration due to gravity is 9.8 m/s^2.

a) What is the ball's speed when it hits the ground?
b) How long after the first ball is thrown should a second ball be simply dropped from the same window so that both balls hit the ground at the same time?

For part a do I calculate the final velocity first? and then use the final velocity as my initial velocity? Should I also change my acceleration to negative?

For the accelerating car at the end of 4 s, I get
d = 20 m/s*4s + (1/2)*2m/s^2*16 s^2
= 96 m, not 56 km
The speed at the end of 4s is correct.
The distance travelled by the first car during this interval is 18*4 = 72 m.
If the first car started 8 m behind, it will be 96 - 72 - 8 = 16 m ahead after 4 seconds. For the next 6 sec, up to t=10, the car separation distance will increase at 10 m/s rate, making the total separation 16 + 60 = 76 m.

For you second problem, part (a), you can use conservation of energy to get the velocity at impact.
(1/2)M V2^2 = (1/2) M V1^2 + MgH
V1 = 2.8 m/s and H = 3.6 m. M cancels out. For part (b), calculate the time it takes the upward-thrown ball to reach the ground. Use a negative value of -g for the acceleration, and a positive intial velocity. The second ball will reach the ground sqrt(2H/g) = 0.86 s after it is released

## Similar Questions

1. ### Physics

Car A is traveling at 84 km/h while Car B is traveling at 58 km/h. What is the relative velocity of Car A to Car B if they both are traveling in the same direction?
2. ### Physics

Car A is traveling at 84 km/h while Car B is traveling at 58 km/h. What is the relative velocity of Car A to Car B if they both are traveling in the same direction?
3. ### Physics

A car starts from rest and accelerates at 5 m/s^2 for 4 s, then maintains that velocity for 3 seconds, then decelerates at the rate of 2m/s^2 for 3 seconds. a) what is the final speed of the car?
4. ### physics

Two cars are traveling in opposite directions on a two lane road. Car A starts from the origin at t =0 and accelerates (moving due East) from rest at 4 m/s2. At t = 0, Car B is moving due West with a velocity of 15 m/s and is 500 m …
5. ### Physics

A truck travels at a constant speed of 28.0 m/s in the fast lane of a two-lane highway. It approaches a stationay car stopped at the side of the road. When the truck is still 1.2x10^2 m behind the car, the car pulls out into the slow …
6. ### physics

A truck is traveling with a uniform velocity 24 m/s, when it passes a car at rest, at this instant the car starts to move and accelerate at the rate of 6m/s^2 in the same direction as the truck. a.) How long will it take the car to …
7. ### physics

The driver of a car wishes to pass a truck that is traveling at a constant speed of 19.0 m/s . Initially, the car is also traveling at a speed 19.0 m/s and its front bumper is a distance 24.3 m behind the truck's rear bumper. The car …
8. ### Physics

A car is travelling at 2 0m/s when it pulls out to pass a truck that is travelling at only 18 m/s the car accelerates at 2 m/s square for 4 sec and then maintains this new velocity. if the car was originally 8 mtrs behind the truck …
9. ### Physical Science

A car of mass m traveling at a velocity of 20m/s east on a straight level road and a truck of mass 2m travelling at 20m/s west on the same road. ignore the effects of friction. calculate the velocity of the truck-car system immediately …
10. ### Physics

A Car is travelling 20m/s when it pulls out to pass a truck that is travelling at 18 m/s. The car accelerates at 2.0m/s^2 for 7.0 seconds B) What is the car's speed at the end of the period of acceleration?

More Similar Questions