This set of Physics Multiple Choice Questions & Answers focuses on “Kinematic Equations for Uniformly Accelerated Motion”.
1. A car moves for 60s covering a distance of 3600m with zero initial velocity. What is the acceleration in m/s2?
Explanation: Here we will use the second equation of motion, s = ut + (1/2)at2. Here, u = 0, s = 3600, t = 60s. On solving, we will get a = 2 m/s2.
2. Number of primary equations of motion is ___
Explanation: There are primarily 3 equations of motion. These are v = u + at, s = ut + (1/2)at2 and v2 = u2 + 2as.
3. A car moves with zero initial velocity up to a velocity of 5 m/s with an acceleration of 10 m/s2. The distance covered is ___
Explanation: Here we will use the third equation of motion. The third equation of motion is v2 = u2 + 2as, u = 0, a = 10, v = 5. Therefore, on solving, we get s = 1.25m.
4. A ball is thrown up with an initial velocity of 20 m/s and after some time it returns. What is the maximum height reached? Take g = 10 m/s2.
Explanation: Here we will use the third equation of motion. The third equation of motion is v2 = u2 + 2as. At the maximum height, the velocity of the ball will be zero, therefore, v = 0, u = 20, and a = -g = -10. On solving, we will get s = 20m.
5. A caterpillar starts travelling at a speed of 1 m/h. If the rate at which the speed changes is 0.1 m/h2, what is the final speed after 10 Hrs?
a) 2 m/h
b) 1 m/h
c) 0.5 m/h
d) 5 m/h
Explanation: We can use the first equation of motion here. The first equation says, v = u + at, here, u = 1 m/h, t = 10 Hrs, a = 0.1 m/h2. On putting all the values in the equation, we will get v = 2 m/h.
6. In the first 10s of a body’s motion, the velocity changes from 10 m/s to 20m/s. During the next 30s the velocity changes from 20m/s to 50m/s. What is the average acceleration in m/s2?
Explanation: Average acceleration is the total change in velocity by the total change in time. Here, total change in velocity = 50-10 = 40m/s, and total change in time = 30+10 =40s. Therefore, average acceleration = 1 m/s2.
7. A body moves a distance of 15 m in a 15mins, with an initial velocity of 0m/min. What is the final velocity in m/min?
Explanation: Use the second equation of motion to find the acceleration. s = ut + (1/2)at2, u = 0, t =15, s=15, therefore, a = 2/15 m/min2. Now use the first equation to find the final velocity. v = u + at, u = 0, t = 15 min, a = 2/15, therefore, v = 2 m/min.
8. 15 m/s can be written in km/h as ______
Explanation: The formula for conversion is, km/h = (18/5) x m/s. Therefore, 15 m/s = 15 x (18/5) = 54 km/h.
9. A coin and a bag full of rocks are thrown in a gravity less environment with the same initial speed. Which one of the following statements is true about the situation?
a) The bag will travel faster
b) The coin will travel faster
c) Both will travel with the same speed
d) Bag will not move
Explanation: Under the application of no external force like gravity, the acceleration is zero. Hence, both the objects will move with the same initial velocity.
10. A bus moves the first few meters of its journey with an acceleration of 5 m/s2 in 10s and the next few meters with an acceleration of 15 m/s2 in 20s. What is the final velocity in m/s if it starts from rest?
Explanation: Apply the first equation of motion in both the parts. For first part, v1 = u + a1t1 = 0 + 5×10 = 50 m/s. For second part, v2 = u2 (= v1) + a2t2 = 50 + 15×20 = 350 m/s.
11. The equations of motion are valid for which of the following types of motion?
a) Constant energy
b) Uniformly accelerated
c) Non-uniformly accelerated
d) Motion along a curve
Explanation: The three equations of motion are valid for uniformly accelerated motion. The equations do not work in situations where the acceleration is non-uniform. In that case it is better to work with the differential forms of velocity and acceleration.
12. In uniformly accelerated motion, how many variables are required to fully describe the system?
Explanation: In uniformly accelerated motion, at least three variables are required to completely define the system This can also be found out by using the equations of motion. For finding out the value of any variable, we need at least three known quantities.
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