Physics - Description of Motion in One Dimension
Exam Duration: 45 Mins Total Questions : 30
With the usual notation, for a uniformly retarded body
- (a)
the formula s = \(\vartheta \)t+\(1\over2\)\(at^{2}\) holds good
- (b)
the formula s = ut+\(1\over2\)\(at^{2}\) holds good
- (c)
the formula \(\vartheta \) = u + at holds good
- (d)
the formula s = \(\vartheta \)t - \(1\over2\)\(at^{2}\) holds good
A body which is uniformly accelerated changes its velocity from 20 m \(s^{-1}\) to 10 m \(s^{-1}\) in 5 secounds while moving in the opposite direction. The total distance travelled in 5 s is ......... and the total displacement is .........
- (a)
\(25\over3\)m and \(125\over3\)m
- (b)
\(100\over3\)m and \(75\over3\)m
- (c)
\(125\over3\)m and \(75\over3\)m
- (d)
\(75\over3\)m and \(25\over3\)m
A car moves for half of its time at 80 km \(km\ h^{-1 2/15}\) and for rest half of time at 40km \(h^{-1}\). Total distance covered is 60 km. What is the average speed of the car ?
- (a)
60 km \(h^{-1}\)
- (b)
80 km \(h^{-1}\)
- (c)
120 km \(h^{-1}\)
- (d)
180 km \(h^{-1}\)
A particle moving in a straight line covers half the distance with speed 3 \(ms^{-1}\). The other half is covered in two equal time intervals with speeds 4.5 \(ms^{-1}\) and 7.5 \(ms^{-1}\), respectively, the average speed of the particle during the motion is
- (a)
4.0 \(ms^{-1}\)
- (b)
5.0 \(ms^{-1}\)
- (c)
5.5 \(ms^{-1}\)
- (d)
4.8 \(ms^{-1}\)
A body moving with a uniform acceleration crosses a distance of 65 m in the 5th second and 105 m in 9th second. How far will it go in 20 s?
- (a)
2040 m
- (b)
240 m
- (c)
2400 m
- (d)
2004 m
A ball is dropped from a bridge 122.5 m above a river. After the ball has been falling for 2s, a second ball is thrown straight down after it. What must its initial velocity be so that both hit the water at the same time?
- (a)
\(26.1\ m/s\)
- (b)
\(29\ m/s\)
- (c)
\(32\ m/s\)
- (d)
\(36\ m/s\)
A particle moves along a straight line such that it displacement at any time t is given by:
s = (t3 - 3t2 + 2)m The displacement when the acceleration becomes zero is:
- (a)
0 m
- (b)
2 m
- (c)
3 m
- (d)
-2 m
A stone is dropped from a rising balloon at a height of 76 m above the ground and reaches the ground in 6 sec. What was
the approximate velocity of the balloon when the stone was dropped?
- (a)
(52/3) m/s upwards
- (b)
(52/3) m/s downwards
- (c)
3 m/s
- (d)
9.8 m/s
The slope of the velocity-time graph for retarded motion is:
- (a)
zero
- (b)
positive
- (c)
negative
- (d)
positive or negative
A person standing on an escalator takes time t1 to reach the top of a tower when the escalator is moving. He takes time t2 to reach the top of the tower when the escalator is standing. How long will he take if he walks up a moving escalator?
- (a)
t2-t1
- (b)
t1+t2
- (c)
t1t2(t1-t2)
- (d)
t1t2(t1+t2)
A thief is running away on a straight road in a jeep moving with a speed of 9 ms-1 A policeman chases him on a motor cycle moving at a speed of 10 ms-1. If the instantaneous separation of the jeep from the motor cycle is 100 m, how long will it take for the policeman to catch the thief?
- (a)
1s
- (b)
19s
- (c)
90s
- (d)
100s
Two particles start moving from the same point along the same straight line. The first moves with constant velocity v and the second with constant acceleration a. During the time that elapses before the second catches the first, the greatest distance between the particles is:
- (a)
\(\frac{v^2}{a}\)
- (b)
\(\frac{v^2}{2a}\)
- (c)
\(\frac{2v^2}{a}\)
- (d)
\(\frac{v^2}{4a}\)
From a height, 3 balls are thrown with speed u, one vertically upward, second horizontally, third downward with times of fall be t1 , t2 and t3 respectively, then:
- (a)
\(t_2=\frac{t_1+t_3}{2}\)
- (b)
\(t_2=\sqrt{t_1t_3}\)
- (c)
\(t_2=\frac{2t_1t_3}{t_1+t_3}\)
- (d)
none of these
A body starts from rest with a uniform acceleration of 2m/ s2 for 10 sec, it moves with constant speed for 30 sec then decelerates by 4 m/s2 to zero. What is the distance covered by the body?
- (a)
750 m
- (b)
850 m
- (c)
600 m
- (d)
None of these
A man, m = 80kg is standing on a trolley of mass 320 kg on a smooth surface. If the man starts walking on the trolley along rails at a speed of 1 ms-1 then after 4 sec, his displacement relative to the ground is:
- (a)
4 m
- (b)
4.8 m
- (c)
3.2 m
- (d)
6 m
Three different objects of masses m1 , m2 and m3 are allowed to fall from rest and from the same point O along three different frictionless paths. The speeds of the three objects on reaching the ground will be in the ratio of:
- (a)
m1:m2:m3
- (b)
m1:2m2:3m3
- (c)
1:1:1
- (d)
\(\frac{1}{m_1}:\frac{1}{m_2}:\frac{1}{m_3}\)
A particle starts from rest and experiences a constant acceleration for 6 seconds. If it travels a distance d1, in the first two seconds, a distance d2 in the next two seconds and a distance d3 in the last two seconds, then:
- (a)
d1:d2:d3=1:1:1
- (b)
d1:d2:d3=1:2:3
- (c)
d1:d2:d3=1:3:5
- (d)
d1:d2:d3=1:5:9
Two bodies A (of mass 1 kg) and B (of mass 3 kg) are dropped from heights of 16 m and 25 m respectively. The ratio of the time taken by them to reach the ground is:
- (a)
4/5
- (b)
5/4
- (c)
12/5
- (d)
5/12
A boat travels 50 km east, then 120 km north and finally it comes back to the starting point through the shortest distance. The total time of journey is 3 hours. What is the average velocity, over the entire trip?
- (a)
0 km h-1
- (b)
100 km h-1
- (c)
17 km h-1
- (d)
33.33 km h-1
- (e)
86.7 km h-1
A particle moving along x-axis has acceleration f at time t, given by:
\(f=f_0(1-\frac{t}{T})\),
where fo and T are constants. The particle at t = 0 has zero velocity. In the time interval between t = 0 and the instant when f = 0, the particle's velocity (vx ) is:
- (a)
1/2 f0T2
- (b)
f0T2
- (c)
1/2 f0T
- (d)
f0T
A ball falls from height h. After 1 second, another ball falls freely from a point 20 m below the point from where the first ball falls. Both of them reach the ground at the same time. What is the value of h?
- (a)
11.2 m
- (b)
21.2 m
- (c)
31.2 m
- (d)
41.2 m
The velocity-time graph for the vertical component of the velocity of a body thrown upwards from the ground and landing on the roof of a building is given in the figure. The height of the building is:
- (a)
50 m
- (b)
40 m
- (c)
20 m
- (d)
30 m
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