Correct answer Carries: 4.
Wrong Answer Carries: -1.
A cyclist moves at a constant speed of \( 7 \, \text{m/s} \) for \( 60 \, \text{s} \). What is the distance covered?
For constant speed, distance \( x = v t \).
Here, \( v = 7 \, \text{m/s} \), \( t = 60 \, \text{s} \).
Substitute: \( x = 7 \cdot 60 = 420 \, \text{m} \).
The distance covered is \( 420 \, \text{m} \).
A car moving at \( 30 \, \text{m/s} \) decelerates uniformly to rest in \( 6 \, \text{s} \). What is the distance covered?
Find \( a = \frac{v - v_0}{t} = \frac{0 - 30}{6} = -5 \, \text{m/s}^2 \).
Use \( x = v_0 t + \frac{1}{2} a t^2 = 30 \cdot 6 + \frac{1}{2} (-5) (6)^2 = 180 - 90 = 90 \, \text{m} \).
The distance covered is \( 90 \, \text{m} \).
A stone falls from a height \( h \) and covers \( 78.4 \, \text{m} \) in the last \( 2 \, \text{s} \) of its fall. What is the total time of fall? (Take \( g = 9.8 \, \text{m/s}^2 \))
Total time = \( t \), last 2 s: \( h = \frac{1}{2} \cdot 9.8 \cdot t^2 \), \( h - 78.4 = \frac{1}{2} \cdot 9.8 \cdot (t - 2)^2 \).
Distance in last 2 s: \( 78.4 = 4.9 [t^2 - (t - 2)^2] \Rightarrow 16 = t^2 - (t^2 - 4t + 4) \Rightarrow 16 = 4t - 4 \Rightarrow t = 5 \, \text{s} \).
A ball is thrown upwards with a speed of \( 42 \, \text{m/s} \). What is the time to reach the maximum height? (Take \( g = 10 \, \text{m/s}^2 \))
At max height, \( v = 0 \). Use \( v = v_0 + a t \).
Here, \( v_0 = 42 \, \text{m/s} \), \( a = -10 \, \text{m/s}^2 \).
Substitute: \( 0 = 42 - 10 t \Rightarrow 10 t = 42 \Rightarrow t = 4.2 \, \text{s} \).
The time taken is \( 4.2 \, \text{s} \).
A ball is thrown upwards with a speed of \( 60 \, \text{m/s} \). What is the time to reach the maximum height? (Take \( g = 10 \, \text{m/s}^2 \))
Here, \( v_0 = 60 \, \text{m/s} \), \( a = -10 \, \text{m/s}^2 \).
Substitute: \( 0 = 60 - 10 t \Rightarrow 10 t = 60 \Rightarrow t = 6 \, \text{s} \).
The time taken is \( 6 \, \text{s} \).
A ball is thrown upwards at \( 15 \, \text{m/s} \) from a \( 45 \, \text{m} \) tower. What is its speed when it passes \( 15 \, \text{m} \) below the tower’s top? (Take \( g = 10 \, \text{m/s}^2 \))
Displacement \( y = -15 \, \text{m} \), \( v^2 = (15)^2 + 2 \cdot 10 \cdot 15 = 225 + 300 = 525 \).
\( v = \sqrt{525} \approx 22.91 \, \text{m/s} \).
A ball is thrown upwards with a speed of \( 52 \, \text{m/s} \). What is the time to reach the maximum height? (Take \( g = 10 \, \text{m/s}^2 \))
Here, \( v_0 = 52 \, \text{m/s} \), \( a = -10 \, \text{m/s}^2 \).
Substitute: \( 0 = 52 - 10 t \Rightarrow 10 t = 52 \Rightarrow t = 5.2 \, \text{s} \).
The time taken is \( 5.2 \, \text{s} \).
A car moving at \( 72 \, \text{km/h} \) decelerates uniformly and stops in \( 8 \, \text{s} \). What is the magnitude of deceleration?
Convert speed: \( 72 \, \text{km/h} = 72 \cdot \frac{1000}{3600} = 20 \, \text{m/s} \).
Use \( a = \frac{v - v_0}{t} \). Here, \( v = 0 \), \( v_0 = 20 \, \text{m/s} \), \( t = 8 \, \text{s} \).
Substitute: \( a = \frac{0 - 20}{8} = -2.5 \, \text{m/s}^2 \).
Magnitude of deceleration is \( 2.5 \, \text{m/s}^2 \).
A cyclist moves at a constant speed of \( 9 \, \text{km/h} \) for \( 20 \, \text{minutes} \). What is the distance covered?
Convert speed: \( 9 \, \text{km/h} = 9 \cdot \frac{1000}{3600} = 2.5 \, \text{m/s} \).
Time = \( 20 \, \text{min} = 20 \cdot 60 = 1200 \, \text{s} \).
Distance \( x = v t = 2.5 \cdot 1200 = 3000 \, \text{m} = 3 \, \text{km} \).
The distance covered is \( 3 \, \text{km} \).
A truck moves at a constant speed of \( 25 \, \text{m/s} \) for \( 20 \, \text{s} \). What is the distance covered?
Here, \( v = 25 \, \text{m/s} \), \( t = 20 \, \text{s} \).
Substitute: \( x = 25 \cdot 20 = 500 \, \text{m} \).
The distance covered is \( 500 \, \text{m} \).
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