Motion Worksheet-7
A. Displacement B. Speed
C. Acceleration D. Velocity
A. mm/s^{2} B. cm s^{–2} C. km/s D. m/s^{2}
A. 1 m/s^{2}. B. -1 m/s^{2}. C. 2 m/s^{2}. D. -2 m/s^{2}.
A. 20 m/s B. 30 m/s C. 10 m/s D. 40 m/s
A. 10 seconds B. 20 seconds
C. 5 seconds D. Body will not stop at all
Answer:
Explanation: Speed is a scalar quantity.
Explanation: Accleration = velocity/time = (displacement/ time)/ time hence the power of time is -2. Which is not there in km/s.
Explanation: First of all we need to convert the given velocity into proper units, that is, we should convert the velocity of 36 kilometres per hour into metres per second.
Now, 1 km = 1000 m
So, 36 km = 36 × 1000 m
= 36,000 m ……..(1)
Also, 1 hour = 60 minutes
= 60 × 60 seconds
= 3600 s ………(2)
So, 36 km per hour
= 10 m/s ……….(3)
Thus, the given velocity of 36 km per hour is equal to 10 metres per second.
Now, initial velocity, u = 0 (second starts from rest)
Final velocity, v = 10 m/s from (3)
Acceleration, a = ?
And, Time, t = 10 s
By putting these values in the first equation of motion :
v = u + at
we get : 10 = 0 + a × 10
10 a = 10
a = 10/10
a = 1 m/s^{2}
Thus, the acceleration is 1 m/s^{2}.
Explanation: In this case the value of retardation is given but in formulas value of acceleration is required. We know that retardation is negative acceleration. So, if the retardation is, +2 m/s^{2} (as given here), then the acceleration will be, -2 m/s^{2} (the minus sign indicates the negative acceleration).
Here, initial velocity, u = ?
Final velocity, v = 0 (As the train stops)
Acceleration, a = -2 m/s^{2}
And, Time, t = 20 s
Now, putting these values in the formula :
v = u + at
We get : 0 = u + (-2) × 20
0 = u – 40
u = 40 m/s
thus, the initial velocity of the train is 40 metres per second.
Explanation: Here, Initial velocity, u = 0.5 m/s
Final velocity, v = 0 (Since the body stops)
Acceleration, a = - 0.05 m/s^{2}
And, Time, t = ?
Now, from the first equation of motion, we have :
v = u + at
so, 0 = 0.5 + (-0.05) × t
or 0.05 t = 0.5
t = (0.5/0.05)
t = 10 s
thus, the body will take 10 seconds to stop.