Question

Part 1 (12 marks): Indicate the answer choice that best completes the statement or answers the question Q1. Which of the following is a scalar quantity? a) weight b) speed c) momentum d) impulse Q2. When you jump on a trampoline straight up you land on the same position. This is because: a) Earth does not move, otherwise the ground will be swept away b) Earth moves very slowly c) your body continues to move with Earth because of its inertia d) the Earth's atmosphere keeps you moving with it Q3. Your mass on planet Mars a) is the same as your mass on Earth b) is less than your mass on Earth c) is greater than your mass on Earth d) depends on the force of gravity on the Mars Q4. Consider a car moving at constant speed in a straight line. Then, the net force acting on the car: a) is zero b) is in the same direction as the direction of motion of the car c) is opposite to the direction of motion of the car d) neither of the above; it depends on the speed of the car 05. A 400 grams book on a table is pushed down by a force of F= 2 N, as shown. The normal (support) force acting on the book is equal to: a) 4 b) 2 N N c) 6 d ) 2.4 N Q6. A car is moving at 126 km/h. What is its speed in m/s? a) 25 m/s b) 35 m/s C) 30 m/s d) 20 m/s Q7. You drive 20 km in 10 minutes and then 30 km in 20 minutes. Your average speed in this trip is a) 50 km/h b) 100 km/h c) 40 km/h d) 166 km/h Q8. A ball is thrown straight upward at 20 m/s. Neglecting air resistance, how long it takes the ball to reach the maximum height? a) 3 seconds b) 4 seconds C) 1 second d) 2 seconds

Answer 1

1) answer is B) since speed does not have any direction, rest all other require direction to describe them.

2) C) since before you jump you were already moving with velocity of earth, hence after jumping your velocity in the direction of earth's velocity doesn't change, and it happens due to property called inertia.

3) A) mass is the fundamental property of the matter, independent of other quantities, such as gravity, speed, acceleration etc. weight will change on Mars but mass will remain same.

4) A) since the speed is constant and the object is moving in a straight line, hence the acceleration is zero. And therefore net force on the object is also zero, by using Newton's second law (i.e F_{​​​​​​net} = m*a_{​​​​​​net} )

5) C) since the net force in vertical direction is zero. And there are three forces acting in vertical direction,

i) gravitational force = m*g = 0.4*10 = 4 N (downwards)

ii) external force = F = 2 N (downwards)

iii) normal = N (upwards)

Hence

N = F + m*g = 2 + 4 = 6 Newtons

6) B) to convert unit Km/hr to m/s you need to multiply the magnitude by 5/18 (1000m/3600sec).

Therefore, (126)*5/18 = 35m/s

7) B) Average speed is given by, total distance travelled divided by total time taken

Total distance = 20 + 30 = 50 km

Total time = 10 + 20 = 30 min = 0.5 hr

Therefore, avg. Speed = 50/0.5 km/hr = 100km/hr

8) D) the object will reach the maximum height when the object's vertical velocity becomes zero.

Using first equation of kinematics in vertical direction,

Where, V = final velocity = 0

U = initial velocity = 20m/s

a = acceleration = -10 m/s^{​​​​​​2}

t = time, which is required to be found

V = U + a*t

0 = 20 + (-10*t)

20 = 10*t

t = 20/10 = 2seconds