Question

1. A car starts from rest and travels for 8.0 s with a uniform acceleration of +1.8 m/s². The driver then applies the brakes, causing a uniform acceleration of −1.5 m/s². If the brakes are applied for 2.0 s, determine each of the following.

(a) How fast is the car going at the end of the braking period? (m/s)

(b) How far has the car gone? (m)

2. A ball is hit with a paddle, causing it to travel straight upward. It takes 3.10 s for the ball to reach its maximum height after being hit. Treat upward as the positive direction.

(a) What is the ball's initial velocity (in m/s), just after it is hit?

(b) What height (in m) does it reach above the level where it was hit?

3. A ball is thrown directly downward with an initial speed of 7.80 m/s, from a height of 29.9 m. After what time interval does it strike the ground? (s)

Answer 1

1.

Consider the accelerating part of the trip

Initial velocity,

acceleration,

time,

Find distance covered and final velocity

Use formula

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Use formula

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Consider the decelerating part

Initial velocity,

acceleration,

time,

Find distance covered and final velocity

Use formula

(a) ANSWER :

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Use formula

Total distance traveled,

(b)ANSWER:

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2.

Given that the ball reached maximum height in 3.10s

(a) What is the ball's initial velocity (in m/s), just after it is hit?

Use formula

At max height vertical velocity becomes zero

ANSWER :

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(b) What height (in m) does it reach above the level where it was hit?

Use formula

ANSWER :

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3. A ball is thrown directly downward with an initial speed of 7.80 m/s, from a height of 29.9 m. After what time interval does it strike the ground? (s)

Given initial velocity,

Initial height,

Use formula

Solve the quadratic equation using a calculator

ANSWER :

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