An object is moving along a straight line. The graph at the right shows its velo

Question

An object is moving along a straight line. The graph at the right shows its velocity as a function of time. During which interval(s) of the graph does the object travel equal distances in equal times? 0 to 2 s 2 s to 3 s 3 s to 5 s 0 to 2 s and 3 s to 5 s 0 to 2 s, 3 to 5 s, and 5 to 6 s During which interval(s) of the graph does the speed of the object increase by equal amounts in equal times? 0 to 2 s 2 s to 3 s 3 s to 5 s 0 to 2 s and 3 s to 5 s 0 to 2 s, 3 to 5 s, and 5 to 6 s How far does the object move from t = 0 to t = 2s? 7.5 m 10 m 15 m 20 m 25 m. What is the acceleration of the object from t = 5 s to t = 6 s? +4 m/s^2 -4 m/s^2 +10 m/s^2 -10 m/s^2 +14 m/s^2 A rock is dropped from rest from a height H above the ground in vacuum. It falls hitting the ground with a of 10 m/s. From what height should it be dropped so that its speed on hitting the ground is 20 m/s? 1.4 H 2 H 3 H 4 H H/1.4 A 5.0 kg rock is dropped from rest down a vertical mineshaft. How long does it takes for the rock to reach a depth of 80m? 2.8 s 4.0 s 4.9 s 8.0 s 9.0 s What height will be reached by a stone thrown straight up with an initial speed of 40 m/s? 41 m 82 m 9 m 164 m 400 m

Explanation / Answer

40)

when the object travels equal distances in equal times , the velocity is constant

constant velocity (slope =0 ) = straight line parallel to time axis

2 to 3s

OPTION (b)

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41)

when the speed increases the slope is costant

0 to 2s   , 3s to 5 s , 5s to 6s

option (e)

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42

distance = area under graph = (1/2)*2*10 = 10 m

option (b)

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43

acceleration a = slope = (10-20)/(6-5) = -10 m/s^2

OPTION (d)

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44)

along vertical

initial velocity voy = 0

ay = - g

vy^2 - voy^2 = 2*ay*dy

for vy = 10 m/s

10^2 - 0 = -2*g*H........(1)

for vy = 20

20^2 - 0 = 2*g*H1........(2)

2 / 1

H1 / H = 400/100

H1 = 4H

OPTION (d)

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45)

along vertical

dy = voy*t + (1/2)*ay*t^2

-80 = 0 - (1/2)*10*t^2

t = 4 s

OPTION (b)

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46)

along vertical

initial velocity voy = 40

final velocity vy = 0

ay = - g

vy^2 - voy^2 = 2*ay*dy

0 - 40^2 = -2*9.8*H

H = 82 m

OPTION (b)

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